RISK FACTORS

Investing in our Class B common stock involves a high degree of risk. You should consider carefully the risks and uncertainties described below, together with all of the other information in this prospectus, including the consolidated financial statements and the related notes included elsewhere in this prospectus, before deciding whether to invest in shares of our Class B common stock. The risks and uncertainties described below are not the only ones we face. Additional risks and uncertainties that we are unaware of may also become important factors that adversely affect our business. If any of the following risks actually occur, our business, financial condition, results of operations and future prospects could be materially and adversely affected. In that event, the market price of our stock could decline, and you could lose part or all of your investment.

Risks Related to Our Business

We have a history of significant losses, which we expect to continue, and we may never achieve or sustain profitability in the future.

We have incurred significant net losses in each fiscal year since our incorporation in 2008 and expect to continue to incur net losses for the foreseeable future. We experienced net losses of $35.0 million during the year ended December 31, 2012 and $62.2 million during the year ended December 31, 2013. As of December 31, 2013, we had an accumulated deficit of $131.2 million. The losses and accumulated deficit were primarily due to the substantial investments we made to grow our business, enhance our technology and offering through research and development and acquire and support customers. We anticipate that cost of revenue and operating expenses will increase substantially in the foreseeable future as we seek to continue to grow our business and acquire customers and develop our platform and new applications. These efforts may prove more expensive than we currently anticipate, and we may not succeed in increasing our revenue sufficiently to offset these higher expenses. Many of our efforts to generate revenue from our business are new and unproven, and any failure to increase our revenue or generate revenue from new applications and services could prevent us from attaining profitability. Furthermore, to the extent we are successful in increasing our customer base, we could also incur increased losses because costs associated with entering into customer agreements are generally incurred up front, while customers are generally billed over the term of the agreement. Our prior losses, combined with our expected future losses, have had and will continue to have an adverse effect on our stockholders’ equity and working capital. We expect to continue to incur operating losses for the foreseeable future and may never become profitable on a quarterly or annual basis, or if we do, we may not be able to sustain profitability in subsequent periods. As a result of these factors, we may need to raise additional capital through debt or equity financings in order to fund our operations, and such capital may not be available on reasonable terms, if at all.

Our limited operating history makes it difficult to evaluate our current business and future prospects and increases the risk of your investment.

We were founded in 2008, began building the first version of Castlight Medical in 2009, did not complete our first customer sale and implementation until 2010 and did not make substantial investments in sales and marketing until 2012. This limited operating history makes our current business and future prospects difficult to evaluate.

We have encountered and will continue to encounter risks and uncertainties frequently experienced by new and growing companies in rapidly changing industries, such as determining appropriate investments of our limited resources, market adoption of our existing and future offerings, competition from other companies, acquiring and retaining customers, managing customer deployments, hiring, integrating, training and retaining skilled personnel, developing new applications and services, determining prices for our applications, unforeseen expenses and challenges in forecasting accuracy. If

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our assumptions regarding these and other similar risks and uncertainties, which we use to plan our business, are incorrect or change as we gain more experience operating our business or due to changes in our industry, or if we do not address these challenges successfully, our operating and financial results could differ materially from our expectations and our business could suffer.

In addition, we may need to change our current operations infrastructure in order for us to achieve profitability and scale our operations efficiently, which makes our future prospects even more difficult to evaluate. For example, in order to grow sales of our Enterprise Healthcare Cloud to smaller customers in a financially sustainable manner, we may need to further automate implementations, tailor our offering and modify our go-to-market approaches to reduce our service delivery and customer acquisition costs. If we fail to implement these changes on a timely basis or are unable to implement them effectively due to our limited experience with the new infrastructure or factors beyond our control, our business may suffer.

The market for our offering is immature and volatile, and if it does not develop, if it develops more slowly than we expect, or if our offering does not drive employee engagement, the growth of our business will be harmed.

The enterprise health care cloud market is new and unproven, and it is uncertain whether it will achieve and sustain high levels of demand and market adoption. Our success will depend to a substantial extent on the willingness of employers to increase their use of our Enterprise Healthcare Cloud offering, the ability of our applications to increase employee engagement, as well as on our ability to demonstrate the value of our offering to customers and their employees and to develop new applications that provide value to customers and users. If employers do not perceive the benefits of our offering or our offering does not drive employee engagement, then our market might not develop at all, or it might develop more slowly than we expect, either of which could significantly adversely affect our operating results. In addition, we have limited insight into trends that might develop and affect our business. We might make errors in predicting and reacting to relevant business, legal and regulatory trends, which could harm our business. If any of these events occur, it could materially adversely affect our business, financial condition or results of operations.

If our security measures are breached and unauthorized access to a customer’s data are obtained, our offering may be perceived as insecure, we may incur significant liabilities, our reputation may be harmed and we could lose sales and customers.

Our offering involves the storage and transmission of customers’ proprietary information, as well as protected health information, or PHI, of our customers and their employees, which is regulated under the Health Insurance Portability and Accountability Act of 1996 and its implementing regulations, collectively HIPAA. Because of the extreme sensitivity of this information, the security features of our offering are very important. If our security measures, some of which are managed by third parties, are breached or fail, unauthorized persons may be able to obtain access to sensitive customer or employee data, including HIPAA-regulated protected health information. A security breach or failure could result from a variety of circumstances and events, including third-party action, employee negligence or error, malfeasance, computer viruses, attacks by computer hackers, failures during the process of upgrading or replacing software, databases or components thereof, power outages, hardware failures, telecommunication failures, user errors, and catastrophic events.

If our security measures were to be breached or fail, our reputation could be severely damaged, adversely affecting customer or investor confidence, customers may curtail their use of or stop using our offering and our business may suffer. In addition, we could face litigation, damages for contract breach, penalties and regulatory actions for violation of HIPAA and other applicable laws or regulations and significant costs for remediation and for measures to prevent future occurrences. In addition, any

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potential security breach could result in increased costs associated with liability for stolen assets or information, repairing system damage that may have been caused by such breaches, incentives offered to customers or other business partners in an effort to maintain the business relationships after a breach and implementing measures to prevent future occurrences, including organizational changes, deploying additional personnel and protection technologies, training employees and engaging third-party experts and consultants. While we maintain insurance covering certain security and privacy damages and claim expenses we may not carry insurance or maintain coverage sufficient to compensate for all liability and in any event, insurance coverage would not address the reputational damage that could result from a security incident.

We outsource important aspects of the storage and transmission of customer information, and thus rely on third parties to manage functions that have material cyber-security risks. These outsourced functions include services such as software design and product development, software engineering, database consulting, call center operations, co-location data centers, data-center security, IT, network security and Web application firewall services. We attempt to address these risks by requiring outsourcing subcontractors who handle customer information to sign business associate agreements contractually requiring those subcontractors to adequately safeguard personal health data and in some cases by requiring such outsourcing subcontractors to undergo third-party security examinations. However, we cannot assure you that these contractual measures and other safeguards will adequately protect us from the risks associated with the storage and transmission of customers proprietary and protected health information.

We may experience cyber-security and other breach incidents that may remain undetected for an extended period. Because techniques used to obtain unauthorized access or to sabotage systems change frequently and generally are not recognized until launched against us, we may be unable to anticipate these techniques or to implement adequate preventive measures. In addition, in the event that our customers authorize or enable third parties to access their data or the data of their employees on our systems, we cannot ensure the complete integrity or security of such data in our systems as we would not control access. If an actual or perceived breach of our security occurs, or if we are unable to effectively resolve such breaches in a timely manner, the market perception of the effectiveness of our security measures could be harmed and we could lose sales and customers.

Our quarterly results may fluctuate significantly, which could adversely impact the value of our Class B common stock.

Our quarterly results of operations, including our revenue, gross margin, net loss and cash flows, may vary significantly in the future, and period-to-period comparisons of our operating results may not be meaningful. Accordingly, our quarterly results should not be relied upon as an indication of future performance. Our quarterly financial results may fluctuate as a result of a variety of factors, many of which are outside of our control, including, without limitation, those listed elsewhere in this “Risk Factors” section and those listed below:

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We are particularly subject to fluctuations in our quarterly results of operations since the costs associated with entering into customer agreements are generally incurred up front, while we generally recognize revenue at launch over the term of the agreement. In addition, some of our contracts with customers provide for one-time bonus payments if our offering achieves certain metrics, such as a certain rate of employee engagement, which may lead to additional fluctuations in our quarterly operating results. In certain contracts, employee engagement may refer to the number of first time registrations by employees of our customers and in other cases it may refer to return usage of our applications by employees. Any fluctuations in our quarterly results may not accurately reflect the underlying performance of our business and could cause a decline in the trading price of our Class B common stock.

If we fail to manage our rapid growth effectively, our expenses could increase more than expected, our revenue may not increase and we may be unable to implement our business strategy.

We have experienced rapid growth in recent periods, which puts strain on our business, operations and employees. For example, we grew from 156 full-time employees at December 31, 2012 to 287 full-time employees at December 31, 2013. We have also signed more than 95 customers in the last two years, increasing the size of our customer base to 106 customers at December 31, 2013; our revenue has increased from $4.2 million for the year ended December 31, 2012 to $13.0 million for the year ended December 31, 2013; and our total backlog, which we define as including both cancellable and non-cancellable portions of our customer agreements that we have not yet billed, has increased from $44.0 million as of December 31, 2012 to $108.7 million as of December 31, 2013. We anticipate that we will continue to rapidly expand our operations. To manage our current and anticipated future growth effectively, we must continue to maintain and enhance our IT infrastructure, financial and accounting systems and controls. We must also attract, train and retain a significant number of qualified sales and marketing personnel, customer support personnel, professional services personnel, software engineers, technical personnel and management personnel, and the availability of such personnel, in particular software engineers, may be constrained. These and similar challenges, and the related costs, may be exacerbated by the fact that our headquarters are located in the San Francisco Bay Area.

A key aspect to managing our growth is our ability to scale our capabilities to implement our offering satisfactorily with respect to both large and demanding enterprise customers, who currently

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comprise the substantial majority of our customer base, as well as smaller customers who are becoming an increasingly larger portion of our customer base. Large customers often require specific features or functions unique to their particular business processes, which at a time of rapid growth or during periods of high demand, may strain our implementation capacity and hinder our ability to successfully implement our offering to our customers in a timely manner. We may also need to make further investments in our technology and automate portions of our offering or services to decrease our costs, particularly as we grow sales of our Enterprise Healthcare Cloud to smaller customers. If we are unable to address the needs of our customers or their employees, or our customers or their employees are unsatisfied with the quality of our offering or services, they may not renew their agreements, seek to cancel or terminate their relationship with us or renew on less favorable terms.

Failure to effectively manage our rapid growth could also lead us to over-invest or under-invest in development and operations, result in weaknesses in our infrastructure, systems or controls, give rise to operational mistakes, financial losses, loss of productivity or business opportunities and result in loss of employees and reduced productivity of remaining employees. Our growth is expected to require significant capital expenditures and might divert financial resources from other projects such as the development of new applications and services. In addition, data and content fees, which are one of our primary operational costs, are not fixed as they vary based on the source and condition of the data we receive from third parties, and if they remain variable or increase over time, we would not be able to realize the economies of scale that we expect as we grow renewals and implementation of new customers, which would negatively impact our gross margin. If our management is unable to effectively manage our growth, our expenses might increase more than expected, our revenue may not increase or might grow more slowly than expected and we might be unable to implement our business strategy. The quality of our offering might also suffer, which could negatively affect our reputation and harm our ability to retain and attract customers.

We incur significant upfront costs in our customer relationships, and if we are unable to maintain and grow these customer relationships over time, we are likely to fail to recover these costs and our operating results will suffer.

We devote significant resources and incur significant upfront costs to establish relationships with our customers and implement our offering and related services. This is particularly so in the case of large enterprises that, to date, have comprised a substantial majority of our customer base and revenue and often request or require specific features or functions unique to their particular business processes. Accordingly, our operating results will depend in substantial part on our ability to deliver a successful customer experience and persuade our customers to maintain and grow their relationship with us over time. For example, if we are not successful in implementing our offering or delivering a successful customer experience, a customer could terminate or fail to renew their agreement with us, we would lose or be unable to recoup the significant upfront costs that we had expended on such customer and our operating results would suffer. As we are growing rapidly, our customer acquisition costs could outpace our build-up of recurring revenue, and we may be unable to reduce our total operating costs through economies of scale such that we are unable to achieve profitability.

Our ability to deliver our full offering to customers depends in substantial part on our ability to access pricing and claims data managed by a limited number of health plans and other third parties.

In order to deliver the full functionality offered by our Enterprise Healthcare Cloud, we need access, on behalf of our customers, to sources of pricing and claims data, much of which is managed by a limited number of health plans and other third parties. We have developed various long-term and short-term data-sharing relationships with certain health plans and other third parties, including most of the largest health plans in the United States. However, we do not currently have a data-sharing

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arrangement with UnitedHealth Group, Inc., one of the largest health plans, as well as other smaller health plans, which limits our ability to offer the full functionality of our offering to customers of such health plans.

The terms of the agreements under which we have access to data managed by health plans and other third parties vary, which can impact the offering we are able to deliver. Many of our agreements with health plans and third parties have terms that limit our access to and permitted uses of claims or pricing data to the data associated with our mutual customers. Also, some agreements may be terminated if the underlying customer contracts do not continue, or may otherwise be subject to termination or non-renewal. In addition, in one agreement with a large national health plan, we agreed, in exchange for more favorable terms to access health care claims data and other strategic benefits, to an exclusivity provision that restricts our ability to provide our full offering to customers of UnitedHealth Group, Inc. until January 2015.

The health plans and other third parties that we currently work with may, in the future, change their position and limit or eliminate our access to pricing and claims data, increase the costs charged to us for access to data, provide data to us in more limited or less useful formats, or restrict our permitted uses of data. Furthermore, some health plans have developed or are developing their own proprietary price and quality estimation tools and may perceive continued cooperation with us as a competitive disadvantage and choose to limit or discontinue our access to pricing and claims data. Failure to continue to maintain and expand our access to pricing and claims data will adversely impact our ability to continue to serve existing customers and expand our offering to new customers.

If our access to pricing and claims data is reduced or becomes more costly to us, our ability to compete in the marketplace or to grow our revenue could be impaired and our operating results would suffer.

If our existing customers do not continue or renew their agreements with us, renew at lower fee levels or decline to purchase additional applications and services from us, our business and operating results will suffer.

We expect to derive a significant portion of our revenue from renewal of existing customer agreements and sales of additional applications and services to existing customers. As a result, achieving a high renewal rate of our customer agreements and selling additional applications and services is critical to our future operating results.

However, we have a limited operating history, and to date have not yet reached the end of the original term for the vast majority of our existing customer agreements. Accordingly, we do not yet have enough experience with customer renewals to predict our customer renewal rate and may experience significantly more difficulty than we anticipate in renewing existing customer agreements. Factors that may affect the renewal rate for our offering and our ability to sell additional applications and services include:

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We enter into master services agreements with our customers. These agreements generally have stated terms of three years. Our customers have no obligation to renew their subscriptions for our offering after the term expires. In addition, our customers may negotiate terms less advantageous to us upon renewal, which may reduce our revenue from these customers. Factors that are not within our control may contribute to a reduction in our contract revenue. For instance, our customers may reduce their number of employees, which would result in a corresponding reduction in the number of employee users eligible for our offering and thus a lower aggregate monthly services fee. Our future operating results also depend, in part, on our ability to sell new applications and services to our existing customers. If our customers fail to renew their agreements, renew their agreements upon less favorable terms or at lower fee levels, or fail to purchase new applications and services from us, our revenue may decline or our future revenue may be constrained.

In addition, a significant number of our customer agreements allow customers to terminate such agreements for convenience at certain times, typically with one to three months advance notice. We typically incur the expenses associated with integrating a customer’s data into our health care database and related training and support prior to recognizing meaningful revenue from such customer. Customer subscription revenue is not recognized until our applications are implemented for launch, which is generally from three to 12 months from contract signing. If a customer terminates its agreement early and revenue and cash flows expected from a customer are not realized in the time period expected or not realized at all, our business, operating results and financial condition could be adversely affected.

A significant portion of our revenue comes from a limited number of customers, the loss of which would adversely affect our financial results.

Historically, we have relied on a limited number of customers for a substantial portion of our total revenue. For the year ended December 31, 2013, the Administrative Committee of the Wal-Mart Stores, Inc., Associates’ Health and Welfare Plan represented approximately 16% of our total revenue. In addition, in our years ended December 31, 2012 and 2013, our top 10 customers accounted for 93% and 61% of our total revenue, respectively. We rely on our reputation and recommendations from key customers in order to promote our offering to potential customers. The loss of any of our key customers, or a failure of some of them to renew or expand user subscriptions, could have a significant impact on the growth rate of our revenue, reputation and our ability to obtain new customers. In addition, mergers and acquisitions involving our customers could lead to cancellation or non-renewal of our agreements with those customers or by the acquiring or combining companies, thereby reducing the number of our existing and potential customers.

Because we generally bill our customers and recognize revenue over the term of the contract, near term declines in new or renewed agreements may not be reflected immediately in our operating results and may be difficult to discern.

Most of our revenue in each quarter is derived from agreements entered into with our customers during previous quarters. Consequently, a decline in new or renewed agreements in any one quarter may not be fully reflected in our revenue for that quarter. Such declines, however, would negatively affect our revenue in future periods and the effect of significant downturns in sales of and market demand for our offering, and potential changes in our rate of renewals or renewal terms, may not be fully reflected in our results of operations until future periods. In addition, we may be unable to adjust our cost structure rapidly, or at all, to take account of reduced revenue. Our subscription model also makes it difficult for us to rapidly increase our total revenue through additional sales in any period, as revenue from new customers must be recognized over the applicable term of the agreement. Accordingly, the effect of changes in the industry impacting our business or changes we experience in our new sales may not be reflected in our short-term results of operations.

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Our sales and implementation cycle can be long and unpredictable and require considerable time and expense, which may cause our operating results to fluctuate.

The sales cycle for our Enterprise Healthcare Cloud offering from initial contact with a potential lead to contract execution and implementation, varies widely by customer, but is typically nine to 24 months. Some of our customers undertake a significant and prolonged evaluation process, including whether our offering meets a customer’s unique health care needs, that frequently involves not only our offering but also those of our competitors, which has in the past resulted in extended sales cycles. Our sales efforts involve educating our customers about the use, technical capabilities and benefits of our offering. Moreover, our large enterprise customers often begin to deploy our service on a limited basis, but nevertheless demand extensive configuration, integration services and pricing concessions, which increase our upfront investment in the sales effort with no guarantee that these customers will deploy our offering widely enough across their organization to justify our substantial upfront investment. It is possible that in the future we may experience even longer sales cycles, more complex customer needs, higher upfront sales costs and less predictability in completing some of our sales as we continue to expand our direct sales force and thereby increase the percentage of our sales personnel with less experience in selling our service, expand into new territories and add additional applications and services. If our sales cycle lengthens or our substantial upfront sales and implementation investments do not result in sufficient sales to justify our investments, our operating results may be harmed.

The health care industry is heavily regulated. Our failure to comply with regulatory requirements could create liability for us, result in adverse publicity and otherwise negatively affect our business.

The health care industry is heavily regulated and is constantly evolving due to the changing political, legislative and regulatory landscape and other factors. Many health care laws are complex, and their application to specific services and relationships may not be clear. Further, some health care laws differ from state to state and it is difficult to ensure our business complies with evolving laws in all states. Our operations may be adversely affected by enforcement initiatives. Our failure to accurately anticipate the application of these laws and regulations to our business, or any other failure to comply with regulatory requirements, could create liability for us, result in adverse publicity and negatively affect our business. For example, failure to comply with these requirements could result in the willingness of current and potential customers to work with us. Federal and state legislatures and agencies periodically consider proposals to revise aspects of the legal rules applicable to the health care industry, or to revise or create additional statutory and regulatory requirements. Such proposals, if implemented, could impact our operations, the use of our offering and our ability to market new applications and services, or could create unexpected liabilities for us. We cannot predict what changes to laws or regulations might be made in the future or how those changes could affect our business or our operating costs.

If we fail to comply with applicable health information privacy and security laws and other state and federal privacy and security laws, we may be subject to significant liabilities, reputational harm and other negative consequences, including decreasing the willingness of current and potential customers to work with us.

We are subject to data privacy and security regulation by both the federal government and the states in which we conduct our business. HIPAA established uniform federal standards for certain “covered entities,” which include health care providers and health plans, governing the conduct of specified electronic health care transactions and protecting the security and privacy of protected health information, or PHI. The Health Information Technology for Economic and Clinical Health Act, or HITECH, which became effective on February 17, 2010, makes HIPAA’s privacy and security standards directly applicable to “business associates,” which are independent contractors or agents of covered entities that create, receive, maintain, or transmit PHI in connection with providing a service for or on

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behalf of a covered entity. HITECH also increased the civil and criminal penalties that may be imposed against covered entities, business associates and other persons, and gave state attorneys general new authority to file civil actions for damages or injunctions in federal courts to enforce HIPAA’s requirements and seek attorney’s fees and costs associated with pursuing federal civil actions.

A portion of the data that we obtain and handle for or on behalf of our customers is considered PHI, subject to HIPAA. Under HIPAA and our contractual agreements with our HIPAA covered entity health plan customers, we are considered a “business associate” to those customers, and are required to maintain the privacy and security of PHI in accordance with HIPAA and the terms of our business associate agreements with customers, including by implementing HIPAA-required administrative, technical and physical safeguards. We have incurred, and will continue to incur, significant costs to establish and maintain these safeguards and, if additional safeguards are required to comply with HIPAA regulations or our customers’ requirements, our costs could increase further, which would negatively affect our operating results. Furthermore, if we fail to maintain adequate safeguards, or we or our agents and subcontractors use or disclose PHI in a manner prohibited or not permitted by HIPAA or our business associate agreements with our customers, or if the privacy or security of PHI that we obtain and handle is otherwise compromised, we could be subject to significant liabilities and consequences, including, without limitation:

Further, we publish statements to end users of our services that describe how we handle and protect personal information. If federal or state regulatory authorities or private litigants consider any portion of these statements to be untrue, we may be subject to claims of deceptive practices, which could lead to significant liabilities and consequences, including, without limitation, costs of responding to investigations, defending against litigation, settling claims and complying with regulatory or court orders.

We also send SMS text messages to potential end users who are eligible to use our service through certain customer and partners. While we get consent from or on behalf of these individuals to send text messages, federal or state regulatory authorities or private litigants may claim that the notices and disclosures we provide, form of consents we obtain or our SMS texting practices are not adequate. These SMS texting campaigns are potential sources of risk for class action lawsuits and liability for our company. Numerous class-action suits under federal and state laws have been filed in the past year against companies who conduct SMS texting programs. Many of those suits have resulted in multi-million dollar settlements to the plaintiffs.

If our new applications and services are not adopted by our customers, or if we fail to continue to innovate and develop new applications and services that are adopted by customers, then our revenue and operating results will be adversely affected.

To date we have derived a substantial majority of our revenue from sales of our Castlight Medical application, and our longer-term operating results and continued growth will depend on our ability to

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successfully develop and sell new applications and services that our customers want and are willing to purchase. In addition to our Castlight Medical application, we have recently introduced a number of new applications, such as our Castlight Pharmacy, Castlight Rewards and Castlight Reference Based Pricing applications, but it is uncertain whether these applications and services will result in significant revenue or comprise a significant portion of our total revenue. In addition, we have invested, and will continue to invest, significant resources in research and development to enhance our existing offering and introduce new high quality applications and services. If existing customers are not willing to make additional payments for such new applications, or if new customers do not value such new applications, our business and operating results will be harmed. If we are unable to predict user preferences or our industry changes, or if we are unable to modify our offering and services on a timely basis, we might lose customers. Our operating results would also suffer if our innovations are not responsive to the needs of our customers, appropriately timed with market opportunity or effectively brought to market.

We operate in a competitive industry, and if we are not able to compete effectively, our business and operating results will be harmed.

While the enterprise health care cloud market is in an early stage of development, the market is competitive and we expect it to attract increased competition, which could make it hard for us to succeed. We currently face competition for sub-components of our offering from a range of companies, including specialized software and solution providers that offer similar solutions, often at substantially lower prices, and that are continuing to develop additional products and becoming more sophisticated and effective. These competitors include Truven Health Analytics Inc., ClearCost Health, Change Healthcare Corporation, Healthcare Blue Book and HealthSparq, Inc. In addition, large, well-financed health plans, with whom we cooperate and on whom we depend in order to obtain the pricing and claims data we need to deliver our offering to customers, have in some cases developed their own cost and quality estimation tools and provide these solutions to their customers at discounted prices or often for free. These health plans include Aetna Inc., Cigna Corporation, UnitedHealth Group, Inc. and WellPoint, Inc. Competition from specialized software and solution providers, health plans and other parties will result in continued pricing pressures, which is likely to lead to price decline in certain product segments, which could negatively impact our sales, profitability and market share. In addition, if health plans perceive continued cooperation with us as a threat to their business interests, they may take steps that impair our access to pricing and claims data, or that otherwise make it more difficult or costly for us to deliver our offering to customers.

Some of our competitors, in particular health plans, have greater name recognition, longer operating histories and significantly greater resources than we do. Furthermore, our current or potential competitors may be acquired by third parties with greater available resources. As a result, our competitors might be able to respond more quickly and effectively than we can to new or changing opportunities, technologies, standards or customer requirements and may have the ability to initiate or withstand substantial price competition. In addition, current and potential competitors have established, and might in the future establish, cooperative relationships with vendors of complementary products, technologies or services to increase the availability of their solutions in the marketplace. Accordingly, new competitors or alliances might emerge that have greater market share, a larger customer base, more widely adopted proprietary technologies, greater marketing expertise, greater financial resources and larger sales forces than we have, which could put us at a competitive disadvantage. Our competitors could also be better positioned to serve certain segments of the enterprise health care cloud market, such as customers that desire a more narrow solution, which could create additional price pressure. In light of these factors, even if our offering is more effective than those of our competitors, current or potential customers might accept competitive offerings in lieu of purchasing our offerings.

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Shifts in health care benefits trends, including any potential decline in the number of self-insured employers, or the emergence of new technologies may render our offering obsolete or require us to expend significant resources in order to remain competitive.

The U.S. health care industry is massive, with a number of large market participants with conflicting agendas, is subject to significant government regulation and is currently undergoing significant change. Changes in our industry, for example, towards private health care exchanges or away from high deductible health plans, or the emergence of new technologies as more competitors enter our market, could result in our offering being less desirable or relevant.

For example, we currently derive substantially all of our revenue from sales to customers that are self-insured employers. The demand for our offering depends on the need of self-insured employers to manage the costs of health care services that they pay on behalf of their employees. While the percentage of employers who are self-insured has been increasing over the past decade, there is no assurance that this trend will continue. Various factors, including changes in the health care insurance market or in government regulation of the health care industry, could cause the percentage of self-insured employers to decline, which would adversely affect the market for our offering and would negatively affect our business and operating results. Furthermore, such trends and our business could be affected by changes in health care spending resulting from the Patient Protection and Affordable Care Act, or the ACA, which was enacted in March 2010 and is currently being implemented. For example, the ACA contemplated the adoption of public exchanges in which consumers can purchase health insurance. In the event that the implementation of the ACA causes our customers to change their health care benefits plans or move to use of exchanges such that it reduces the need for our offering, or if the number of self-insured employers otherwise declines, we would be forced to compete on additional application and service attributes or to expend significant resources in order to alter our offering to remain competitive.

If health care benefits trends shift or entirely new technologies are developed that replace existing offerings, our existing or future offerings could be rendered obsolete and our business could be adversely affected. In addition, we may experience difficulties with software development, industry standards, design or marketing that could delay or prevent our development, introduction or implementation of new applications and enhancements.

We may require additional capital to support business growth, and this capital might not be available to us on acceptable terms or at all.

Our operations have consumed substantial amounts of cash since inception and we intend to continue to make significant investments to support our business growth, respond to business challenges or opportunities, develop new applications and services, enhance our existing offering and services, enhance our operating infrastructure and potentially acquire complementary businesses and technologies. For the years ended December 31, 2012 and 2013, our net cash used in operating activities was $29.3 million and $50.1 million, respectively. As of December 31, 2013, we had $67.2 million of cash, cash equivalents and marketable securities, which are held for working capital purposes. Our future capital requirements may be significantly different from our current estimates and will depend on many factors including our growth rate, subscription renewal activity, the timing and extent of spending to support development efforts, the expansion of sales and marketing activities, the introduction of new and enhanced services offerings and the continuing market acceptance of our cloud-based subscription services. Accordingly, we might need to engage in equity or debt financings or collaborative arrangements to secure additional funds. If we raise additional funds through further issuances of equity or convertible debt securities, our existing stockholders could suffer significant dilution, and any new equity securities we issue could have rights, preferences and privileges superior to those of holders of our common stock. Any debt financing secured by us in the future could involve

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restrictive covenants relating to our capital-raising activities and other financial and operational matters, which might make it more difficult for us to obtain additional capital and to pursue business opportunities, including potential acquisitions. We might have to obtain funds through arrangements with collaborative partners or others that may require us to relinquish rights to our technologies or offering that we otherwise would not relinquish. In addition, during the recent economic instability, it has been difficult for many companies to obtain financing in the public markets or to obtain debt financing, and we might not be able to obtain additional financing on commercially reasonable terms, if at all. If we are unable to obtain adequate financing or financing on terms satisfactory to us when we require it, our ability to continue to support our business growth and to respond to business challenges could be significantly limited.

Our proprietary software may not operate properly, which could damage our reputation, give rise to claims against us or divert application of our resources from other purposes, any of which could harm our business and operating results.

Proprietary software development is time-consuming, expensive and complex, and may involve unforeseen difficulties. We may encounter technical obstacles, and it is possible that we discover additional problems that prevent our proprietary applications from operating properly. We are currently implementing software with respect to a number of new applications and services, including our Castlight Pharmacy, Castlight Rewards and Castlight Reference Based Pricing applications. If our offering does not function reliably or fails to achieve client expectations in terms of performance, clients could assert liability claims against us or attempt to cancel their contracts with us. This could damage our reputation and impair our ability to attract or maintain clients.

Moreover, data services are complex as those we offer have in the past contained, and may in the future develop or contain, undetected defects or errors. Material performance problems, defects or errors in our existing or new software and applications and services may arise in the future and may result from interface of our offering with systems and data that we did not develop and the function of which is outside of our control or undetected in our testing. These defects and errors and any failure by us to identify and address them could result in loss of revenue or market share, diversion of development resources, injury to our reputation and increased service and maintenance costs. Defects or errors in our Enterprise Healthcare Cloud might discourage existing or potential clients from purchasing our offering from us. Correction of defects or errors could prove to be impossible or impracticable. The costs incurred in correcting any defects or errors may be substantial and could adversely affect our operating results.

If we cannot implement our offering for customers in a timely manner, we may lose customers and our reputation may be harmed.

Our customers have a variety of different data formats, enterprise applications and infrastructure and our offering must support our customers’ data formats and integrate with complex enterprise applications and infrastructures. If our platform does not currently support a customer’s required data format or appropriately integrate with a customer’s applications and infrastructure, then we must configure our platform to do so, which increases our expenses. Additionally, we do not control our customers’ implementation schedules. As a result, if our customers do not allocate internal resources necessary to meet their implementation responsibilities or if we face unanticipated implementation difficulties, the implementation may be delayed. Further, our implementation capacity has at times constrained our ability to successfully implement our offering for our customers in a timely manner, particularly during periods of high demand. If the customer implementation process is not executed successfully or if execution is delayed, we could incur significant costs, customers could become dissatisfied and decide not to increase usage of our offering, or not to use our offering beyond an initial period prior to their term commitment or, in some cases, revenue recognition could be delayed. In

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addition, competitors with more efficient operating models with lower implementation costs could penetrate our customer relationships.

Additionally, large and demanding enterprise customers, who currently comprise the substantial majority of our customer base, may request or require specific features or functions unique to their particular business processes, which increase our upfront investment in sales and deployment efforts and the revenue resulting from the customers under our typical contract length may not cover the upfront investments. If prospective large customers require specific features or functions that we do not offer, then the market for our offering will be more limited and our business could suffer.

In addition, supporting large customers could require us to devote significant development services and support personnel and strain our personnel resources and infrastructure. Furthermore, if we are unable to address the needs of these customers in a timely fashion or further develop and enhance our offering, or if a customer or its employees is not satisfied with the quality of work performed by us or with the offering delivered or professional services rendered, then we could incur additional costs to address the situation, we may be required to issue credits or refunds for pre-paid amounts related to unused services, the profitability of that work might be impaired and the customer’s dissatisfaction with our offering could damage our ability to expand the number of applications and services purchased by that customer. These customers may not renew their agreements, seek to terminate their relationship with us or renew on less favorable terms. Moreover, negative publicity related to our customer relationships, regardless of its accuracy, may further damage our business by affecting our ability to compete for new business with current and prospective customers. If any of these were to occur, our revenue may decline and our operating results could be adversely affected.

Any failure to offer high-quality technical support services may adversely affect our relationships with our customers and harm our financial results.

Our customers depend on our support organization to resolve any technical issues relating to our offering. In addition, our sales process is highly dependent on the quality of our offering, our business reputation and on strong recommendations from our existing customers. Any failure to maintain high-quality and highly-responsive technical support, or a market perception that we do not maintain high-quality and highly-responsive support, could harm our reputation, adversely affect our ability to sell our offering to existing and prospective customers, and harm our business, operating results and financial condition.

We offer technical support services with our offering and may be unable to respond quickly enough to accommodate short-term increases in customer demand for support services, particularly as we increase the size of our customer base. We also may be unable to modify the format of our support services to compete with changes in support services provided by competitors. It is difficult to predict customer demand for technical support services and if customer demand increases significantly, we may be unable to provide satisfactory support services to our customers and their employees. Additionally, increased customer demand for these services, without corresponding revenue, could increase costs and adversely affect our operating results.

We depend on data centers operated by third parties for our offering, and any disruption in the operation of these facilities could adversely affect our business.

We provide our Enterprise Healthcare Cloud through computer hardware that is currently located in a third-party data center in Texas, which is operated by one IT hosting company, and two third-party data centers in Colorado and Arizona, which are operated by a second IT hosting company. We expect to transition all of our hardware to the data centers in Colorado and Arizona by the end of 2014. While we control and have access to our servers and all of the components of our network that are located in our external data centers, we do not control the operation of these facilities. The owners of our data centers have no obligation to renew their agreements with us on commercially reasonable terms, or at

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all. If we are unable to renew these agreements on commercially reasonable terms, or if our data center operator is acquired, we may be required to transfer our servers and other infrastructure to new data center facilities, and we may incur significant costs and possible service interruption in connection with doing so.

Problems faced by our third-party data center locations could adversely affect the experience of our customers. The operators of the data centers could decide to close their facilities without adequate notice. In addition, any financial difficulties, such as bankruptcy, faced by the operators of the data centers or any of the service providers with whom we or they contract may have negative effects on our business, the nature and extent of which are difficult to predict. Additionally, if our data centers are unable to keep up with our growing needs for capacity, this could have an adverse effect on our business. For example, a rapid expansion of our business could affect the service levels at our data centers or cause such data centers and systems to fail. Any changes in third-party service levels at our data centers or any disruptions or other performance problems with our offering could adversely affect our reputation and may damage our customers’ stored files or result in lengthy interruptions in our services. Interruptions in our services might reduce our revenue, cause us to issue refunds to customers for prepaid and unused subscriptions, subject us to potential liability or adversely affect our renewal rates.

The information that we provide to our customers, and their employees and families, could be inaccurate or incomplete, which could harm our business, financial condition and results of operations.

We provide price, quality and other health care-related information for use by our customers, and their employees and families, to search and compare options for health care services. Third-party health plans and our clients provide us with most of these data. Because data in the health care industry is fragmented in origin, inconsistent in format and often incomplete, the overall quality of data in the health care industry is poor, and we frequently discover data issues and errors. If the data that we provide to our customers are incorrect or incomplete or if we make mistakes in the capture or input of these data, our reputation may suffer and our ability to attract and retain customers may be harmed.

In addition, a court or government agency may take the position that our storage and display of health information exposes us to personal injury liability or other liability for wrongful delivery or handling of health care services or erroneous health information. While we maintain insurance coverage, this coverage may prove to be inadequate or could cease to be available to us on acceptable terms, if at all. Even unsuccessful claims could result in substantial costs and diversion of management resources. A claim brought against us that is uninsured or under-insured could harm our business, financial condition and results of operations.

We depend on our senior management team, and the loss of one or more of our executive officers or key employees or an inability to attract and retain highly skilled employees could adversely affect our business.

Our success depends largely upon the continued services of our key executive officers. These executive officers are at-will employees and therefore may terminate employment with us at any time with no advance notice. We do not maintain “key person” insurance for any of these executive officers or any of our other key employees. We also rely on our leadership team in the areas of research and development, marketing, services and general and administrative functions. From time to time, there may be changes in our executive management team resulting from the hiring or departure of executives, which could disrupt our business. The replacement of one or more of our executive officers or other key employees would likely involve significant time and costs and may significantly delay or prevent the achievement of our business objectives.

To continue to execute our growth strategy, we also must attract and retain highly skilled personnel. Competition is intense for engineers with high levels of experience in designing and

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developing software and Internet-related services, particularly in the San Francisco Bay Area where we are located. We might not be successful in maintaining our unique culture and continuing to attract and retain qualified personnel. We have from time to time in the past experienced, and we expect to continue to experience in the future, difficulty in hiring and retaining highly skilled personnel with appropriate qualifications. The pool of qualified personnel with Software-as-a-Service, or SaaS, experience or experience working with the health care market is limited overall. In addition, many of the companies with which we compete for experienced personnel have greater resources than we have.

In addition, in making employment decisions, particularly in the Internet and high-technology industries, job candidates often consider the value of the stock options or other equity instruments they are to receive in connection with their employment. Volatility in the price of our stock might, therefore, adversely affect our ability to attract or retain highly skilled personnel. Furthermore, the requirement to expense stock options and other equity instruments might discourage us from granting the size or type of stock option or equity awards that job candidates require to join our company. If we fail to attract new personnel or fail to retain and motivate our current personnel, our business and future growth prospects could be severely harmed.

If we cannot maintain our corporate culture as we grow, we could lose the transparency, courage, community, passion and excellence that we believe contribute to our success and our business may be harmed.

We believe that a critical asset for our business, and a source of our competitive strength, is our unique company culture, which we believe fosters transparency, courage, community, passion and excellence. As we grow and change, we may find it difficult to maintain these important aspects of our corporate culture. Any failure to preserve our culture could also negatively affect our ability to attract and retain personnel, our reputation and our ability to continue to build and advance our offering and may otherwise adversely affect our future success.

If we fail to develop widespread brand awareness cost-effectively, our business may suffer.

We believe that developing and maintaining widespread awareness of our brand in a cost-effective manner is critical to achieving widespread adoption of our offering and attracting new customers. Brand promotion activities may not generate customer awareness or increase revenue, and even if they do, any increase in revenue may not offset the expenses we incur in building our brand. If we fail to successfully promote and maintain our brand, or incur substantial expenses, we may fail to attract or retain customers necessary to realize a sufficient return on our brand-building efforts, or to achieve the widespread brand awareness that is critical for broad customer adoption of our offering.

Our marketing efforts depend significantly on our ability to receive positive references from our existing customers.

Our marketing efforts depend significantly on our ability to call on our current customers to provide positive references to new, potential customers. Given our limited number of long-term customers, the loss or dissatisfaction of any customer could substantially harm our brand and reputation, inhibit the market adoption of our offering and impair our ability to attract new customers and maintain existing customers. Any of these consequences could have a material adverse effect on our business, financial condition and results of operations.

Any failure to protect our intellectual property rights could impair our ability to protect our proprietary technology and our brand.

Our success depends in part on our ability to enforce our intellectual property and other proprietary rights. We rely upon a combination of patent, trademark, copyright and trade secret laws,

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as well as license and access agreements and other contractual provisions, to protect our intellectual property and other proprietary rights. In addition, we attempt to protect our intellectual property and proprietary information by requiring certain of our employees, consultants and contractors to enter into confidentiality, noncompetition and assignment of inventions agreements. These laws, procedures and restrictions provide only limited protection and any of our intellectual property rights may be challenged, invalidated, circumvented, infringed or misappropriated. While we have four U.S. patent applications pending, and we currently have one issued U.S. patent, we cannot ensure that any of our pending patent applications will be granted or that our issued patent will adequately protect our intellectual property. In addition, if any patents are issued in the future, they may not provide us with any competitive advantages, or may be successfully challenged by third parties. To the extent that our intellectual property and other proprietary rights are not adequately protected, third parties might gain access to our proprietary information, develop and market solutions similar to ours, or use trademarks similar to ours, each of which could materially harm our business. Further, unauthorized parties may attempt to copy or obtain and use our technology to develop applications with the same functionality as our offering, and policing unauthorized use of our technology and intellectual property rights is difficult and may not be effective. The failure to adequately protect our intellectual property and other proprietary rights could materially harm our business.

We could incur substantial costs as a result of any claim of infringement of another party’s intellectual property rights.

In recent years, there has been significant litigation in the United States involving patents and other intellectual property rights. Companies in the Internet and technology industries are increasingly bringing and becoming subject to suits alleging infringement of proprietary rights, particularly patent rights, and our competitors and other third parties may hold patents or have pending patent applications, which could be related to our business. These risks have been amplified by the increase in third parties, which we refer to as non-practicing entities, whose sole primary business is to assert such claims. We expect that we may receive in the future notices that claim we or our customers using our offering have misappropriated or misused other parties’ intellectual property rights, particularly as the number of competitors in our market grows and the functionality of applications amongst competitors overlaps. If we are sued by a third party that claims that our technology infringes its rights, the litigation, whether or not successful, could be extremely costly to defend, divert our management’s time, attention and resources, damage our reputation and brand and substantially harm our business. We do not currently have an extensive patent portfolio of our own, which may limit the defenses available to us in any such litigation.

In addition, in most instances, we have agreed to indemnify our customers against certain third-party claims, which may include claims that our offering infringes the intellectual property rights of such third parties. Our business could be adversely affected by any significant disputes between us and our customers as to the applicability or scope of our indemnification obligations to them. The results of any intellectual property litigation to which we might become a party, or for which we are required to provide indemnification, may require us to do one or more of the following:

If we are required to make substantial payments or undertake any of the other actions noted above as a result of any intellectual property infringement claims against us or any obligation to

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indemnify our customers for such claims, such payments or costs could have a material adverse effect upon our business and financial results.

Our use of open source technology could impose limitations on our ability to commercialize our software platform.

Our offering incorporates open source software components that are licensed to us under various public domain licenses. Some open source software licenses require users who distribute open source software as part of their software to publicly disclose all or part of the source code to such software or make available any derivative works of the open source code on unfavorable terms or at no cost. There is little or no legal precedent governing the interpretation of many of the terms of these licenses and therefore the potential impact of such terms on our business is somewhat unknown. There is a risk that such licenses could be construed in a manner that imposes unanticipated conditions or restrictions on our ability to market our software platform. While we monitor our use of open source software and try to ensure that none is used in a manner that would require us to disclose our source code or that would otherwise breach the terms of an open source agreement, such use could inadvertently occur and we may be required to release our proprietary source code, pay damages for breach of contract, re-engineer our offering, discontinue sales of our offering in the event re-engineering cannot be accomplished on a timely basis or take other remedial action that may divert resources away from our development efforts, any of which could cause us to breach customer contracts, harm our reputation, result in customer losses or claims, increase our costs or otherwise adversely affect our business and operating results.

We may acquire other companies or technologies, which could divert our management’s attention, result in dilution to our stockholders and otherwise disrupt our operations and adversely affect our operating results.

We may in the future seek to acquire or invest in businesses, applications and services or technologies that we believe could complement or expand our offering, enhance our technical capabilities or otherwise offer growth opportunities. The pursuit of potential acquisitions may divert the attention of management and cause us to incur various expenses in identifying, investigating and pursuing suitable acquisitions, whether or not they are consummated.

In addition, we have limited experience in acquiring other businesses. If we acquire additional businesses, we may not be able to integrate the acquired personnel, operations and technologies successfully, or effectively manage the combined business following the acquisition. We also may not achieve the anticipated benefits from the acquired business due to a number of factors, including:

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In addition, a significant portion of the purchase price of companies we acquire may be allocated to acquired goodwill and other intangible assets, which must be assessed for impairment at least annually. In the future, if our acquisitions do not yield expected returns, we may be required to take charges to our operating results based on this impairment assessment process, which could adversely affect our results of operations.

Acquisitions could also result in dilutive issuances of equity securities or the incurrence of debt, which could adversely affect our operating results. In addition, if an acquired business fails to meet our expectations, our operating results, business and financial position may suffer.

If we are unable to implement and maintain effective internal control over financial reporting in the future, investors may lose confidence in the accuracy and completeness of our financial reports and the market price of our Class B common stock may be negatively affected.

As a public company, we will be required to maintain internal control over financial reporting and to report any material weaknesses in such internal control. Section 404 of the Sarbanes-Oxley Act of 2002, or the Sarbanes-Oxley Act, requires that we evaluate and determine the effectiveness of our internal control over financial reporting and, beginning with our annual report for the fiscal year ending December 31, 2015, provide a management report on the internal control over financial reporting. Our independent registered public accounting firm is not required to audit the effectiveness of our internal control over financial reporting until after we are no longer an “emerging growth company,” as defined in the JOBS Act. At such time, our independent registered public accounting firm may issue a report that is adverse in the event it is not satisfied with the level at which our internal control over financial reporting is documented, designed or operating. If we have a material weakness in our internal control over financial reporting, we may not detect errors on a timely basis and our financial statements may be materially misstated. We are in the process of designing and implementing the internal control over financial reporting required to comply with this obligation, which process will be time consuming, costly and complicated. If we identify material weaknesses in our internal control over financial reporting, if we are unable to comply with the requirements of Section 404 in a timely manner, if we are unable to assert that our internal control over financial reporting is effective, or if our independent registered public accounting firm is unable to express an opinion as to the effectiveness of our internal control over financial reporting, investors may lose confidence in the accuracy and completeness of our financial reports, the market price of our Class B common stock could be negatively affected and we could become subject to investigations by the New York Stock Exchange, on which our securities are listed, the SEC or other regulatory authorities, which could require us to obtain additional financial and management resources.

We will incur significantly increased costs and devote substantial management time as a result of operating as a public company.

As a public company, we will incur significant legal, accounting and other expenses that we did not incur as a private company. For example, we will be subject to the reporting requirements of the Exchange Act and will be required to comply with the applicable requirements of the Sarbanes-Oxley Act and the Dodd-Frank Wall Street Reform and Consumer Protection Act, as well as rules and regulations subsequently implemented by the SEC and the New York Stock Exchange, including the establishment and maintenance of effective disclosure and financial controls, changes in corporate governance practices and required filing of annual, quarterly and current reports with respect to our

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business and operating results. We expect that compliance with these requirements will increase our legal and financial compliance costs and will make some activities more time consuming and costly. In addition, we expect that our management and other personnel will need to divert attention from operational and other business matters to devote substantial time to these public company requirements. In particular, we expect to incur significant expenses and devote substantial management effort toward ensuring compliance with the requirements of Section 404 of the Sarbanes-Oxley Act, which will increase when we are no longer an emerging growth company, as defined by the JOBS Act. We may also need to hire additional accounting and financial staff with appropriate public company experience and technical accounting knowledge and may need to establish an internal audit function.

We also expect that operating as a public company will make it more expensive for us to obtain director and officer liability insurance, and we may be required to accept reduced coverage or incur substantially higher costs to obtain coverage. This could also make it more difficult for us to attract and retain qualified people to serve on our board of directors, our board committees or as executive officers.

We are an emerging growth company and we cannot be certain if the reduced disclosure requirements applicable to emerging growth companies will make our Class B common stock less attractive to investors.

We are an emerging growth company, as defined under the JOBS Act. For as long as we continue to be an emerging growth company, we intend to take advantage of certain exemptions from various reporting requirements that are applicable to other public companies including, but not limited to, reduced disclosure obligations regarding executive compensation in our periodic reports and proxy statements and exemptions from the requirements of holding a nonbinding advisory vote on executive compensation and stockholder approval of any golden parachute payments not previously approved. We cannot predict if investors will find our Class B common stock less attractive because we will rely on these exemptions. If some investors find our Class B common stock less attractive as a result, there may be a less active trading market for our Class B common stock and our stock price may be more volatile.

We will remain an emerging growth company until the earliest of (i) the end of the fiscal year in which the market value of our Class B common stock that is held by non-affiliates exceeds $700 million as of June 30, (ii) the end of the fiscal year in which we have total annual gross revenue of $1 billion or more during such fiscal year, (iii) the date on which we issue more than $1 billion in non-convertible debt in a three-year period or (iv) December 31, 2019, which is the last day of the fiscal year following five years from the date of this prospectus.

We may not be able to utilize a significant portion of our net operating loss or research tax credit carryforwards, which could adversely affect our profitability.

As of December 31, 2013, we had federal and state net operating loss carryforwards of $120.7 million and $97.8 million, respectively, due to prior period losses, which if not utilized will begin to expire in 2028 for federal and state purposes. We also have federal and state research tax credit carryforwards of $2.1 million and $2.3 million as of December 31, 2013, respectively, which if not utilized will begin to expire in 2028 for federal purposes. These net operating loss and research tax credit carryforwards could expire unused and be unavailable to offset future income tax liabilities, which could adversely affect our profitability.

In addition, under Section 382 of the Internal Revenue Code of 1986, as amended, our ability to utilize net operating loss carryforwards or other tax attributes, such as research tax credits, in any taxable year may be limited if we experience an “ownership change.” A Section 382 “ownership change” generally occurs if one or more stockholders or groups of stockholders who own at least 5% of

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our stock increase their ownership by more than 50 percentage points over their lowest ownership percentage within a rolling three-year period. Similar rules may apply under state tax laws. This offering or future issuances of our stock could cause an “ownership change.” Any future ownership change, which could be outside of our control, could also have a material effect on the use of our net operating loss carryforwards or other tax attributes, which could adversely affect our profitability.

We may be subject to liabilities with respect to sales and use, value added and similar taxes, which could adversely affect our results of operations.

We are typically held responsible by taxing authorities for the collection and payment of any applicable sales and use, value added and similar taxes on the subscriptions and services that we sell. Prior to 2014, we did not collect or remit U.S. state taxes on the charges to our customers for our subscriptions or services. In 2014, we will begin to collect sales tax relating to subscription and services fees. Historically, we have recorded a contingent sales tax liability for sales including estimated penalties and interest. If our ultimate liability exceeds such amount, it could result in charges to our earnings. Each state has different rules and regulations governing sales and use, value added and similar taxes, and these rules and regulations are subject to varying interpretations that change over time. Certain jurisdictions in which we did not collect such taxes may assert that such taxes are applicable, which could result in tax assessments, penalties and interest, and we may be required to collect such taxes in the future. Such tax assessments, penalties and interest, or future requirements may adversely affect our results of operations. Moreover, imposition of such taxes on us going forward will effectively increase the cost of our applications and services to our customers and might adversely affect our ability to retain existing customers or to gain new customers in the areas in which such taxes are imposed.

Economic uncertainties or downturns in the general economy or the industries in which our customers operate could disproportionately affect the demand for our offering and negatively impact our results of operations.

General worldwide economic conditions have experienced a significant downturn, and market volatility and uncertainty remain widespread, making it extremely difficult for our customers and us to accurately forecast and plan future business activities. In addition, these conditions could cause our customers or prospective customers to decrease headcount, benefits or human resources budgets, which could decrease corporate spending on our applications and services, resulting in delayed and lengthened sales cycles, a decrease in new customer acquisition and loss of customers. Furthermore, during challenging economic times, our customers may have difficulty gaining timely access to sufficient credit or obtaining credit on reasonable terms, which could impair their ability to make timely payments to us and adversely affect our revenue. If that were to occur, our financial results could be harmed. Further, challenging economic conditions might impair the ability of our customers to pay for the applications and services they already have purchased from us and, as a result, our write-offs of accounts receivable could increase. We cannot predict the timing, strength, or duration of any economic slowdown or recovery. If the condition of the general economy or markets in which we operate worsens, our business could be harmed.

The estimates of market opportunity and forecasts of market growth included in this prospectus may prove to be inaccurate, and even if the market in which we compete achieves the forecasted growth, our business could fail to grow at similar rates, if at all.

Market opportunity estimates and growth forecasts are subject to significant uncertainty and are based on assumptions and estimates that may not prove to be accurate. The estimates and forecasts in this prospectus relating to the size and expected growth of the enterprise health care cloud market may prove to be inaccurate. Even if the market in which we compete meets our size estimates and forecasted growth, our business could fail to grow at similar rates, if at all. For more information

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regarding our estimates of market opportunity and the forecasts of market growth included in this prospectus, see the section titled “Industry and Market Data.”

Natural or man-made disasters and other similar events may significantly disrupt our business and negatively impact our results of operations and financial condition.

Our offices may be harmed or rendered inoperable by natural or man-made disasters, including earthquakes, power outages, fires, floods, nuclear disasters and acts of terrorism or other criminal activities, which may render it difficult or impossible for us to operate our business for some period of time. For example, our headquarters are located in the San Francisco Bay Area, a region known for seismic activity. Any disruptions in our operations related to the repair or replacement of our office, could negatively impact our business and results of operations and harm our reputation. In addition, we may not carry business insurance sufficient to compensate for losses that may occur. Any such losses or damages could have a material adverse effect on our business, results of operations and financial condition. In addition, the facilities of significant customers, health plans or major strategic partners may be harmed or rendered inoperable by such natural or man-made disasters, which may cause disruptions, difficulties or material adverse effects on our business.

Risks Related to This Offering and Ownership of Our Class B Common Stock

The stock price of our Class B common stock may be volatile or may decline regardless of our operating performance, and you may not be able to resell your shares at or above the initial public offering price.

The market price of our Class B common stock may fluctuate significantly. These fluctuations could cause you to lose all or part of your investment in our common stock since you might be unable to sell your shares at or above the price you paid in this offering. Factors, many of which are beyond our control, that could cause fluctuations in the market price of our Class B common stock include the following:

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In addition, the stock markets have experienced extreme price and volume fluctuations that have affected and continue to affect the market prices of equity securities of many technology companies. Stock prices of many technology companies have fluctuated in a manner unrelated or disproportionate to the operating performance of those companies. In the past, stockholders have filed securities class action litigation following periods of market volatility. If we were to become involved in securities litigation, it could subject us to substantial costs, divert resources and the attention of management from our business and adversely affect our business.

Substantial blocks of our total outstanding shares may be sold into the market when lock-up or market standoff periods end. If there are substantial sales of shares of our Class B common stock, the price of our Class B common stock could decline.

The price of our Class B common stock could decline if there are substantial sales of our Class B common stock, particularly sales by our directors, executive officers and significant stockholders, or if there is a large number of shares of our Class B common stock available for sale. All of the shares of Class B common stock sold in this offering will be available for sale in the public market. Any shares of Class B common stock that may be outstanding as of the date of this offering will be restricted from resale as a result of market standoff and “lock-up” agreements, as more fully described in “Shares Eligible for Future Sale.” These shares will become available to be sold 181 days after the date of this prospectus. Shares held by directors, executive officers and other affiliates will be subject to volume limitations under Rule 144 under the Securities Act and various vesting agreements.

After the consummation of this offering, certain of our stockholders will have rights, subject to some conditions, to require us to file registration statements covering their shares and to include their shares in registration statements that we may file for ourselves or our stockholders. All of the shares held by these holders are subject to market standoff or lock-up agreements restricting their sale until 181 days after the date of this prospectus. We also intend to register shares of Class B common stock that we have issued and may issue under our employee equity incentive and employee stock purchase plans. Once we register these shares, they will be able to be sold freely in the public market upon issuance, subject to existing market standoff or lock-up agreements.

Goldman, Sachs & Co. and Morgan Stanley & Co. LLC may, at their discretion, permit our stockholders to sell shares prior to the expiration of the restrictive provisions contained in the lock-up agreements.

The market price of the shares of our Class B common stock could decline as a result of the sale of a substantial number of our shares of Class B common stock in the public market or the perception in the market that the holders of a large number of shares intend to sell their shares.

There has been no prior public market for our Class B common stock and an active trading market may not develop or be sustained.

There has been no public market for our Class B common stock prior to this offering. The initial public offering price for our Class B common stock will be determined through negotiations between the underwriters and us and may vary from the market price of our Class B common stock following this offering. An active or liquid market in our Class B common stock may not develop upon closing of this offering or, if it does develop, it may not be sustainable. The lack of an active market may impair

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the value of your shares, your ability to sell your shares at the time you wish to sell them and the prices that you may obtain for your shares. An inactive market may also impair our ability to raise capital by selling our Class B common stock and may impair our ability to acquire other companies, products or technologies by using our Class B common stock as consideration.

The dual class structure of our common stock will have the effect of concentrating voting control with our executive officers (including our Chief Executive Officer) and directors and their affiliates; this will limit or preclude your ability to influence corporate matters.

Each share of Class A common stock and each share of Class B common stock has one vote per share, except on the following matters (in which each share of Class A common stock has ten votes per share and each share of Class B common stock has one vote per share):

Because of our dual class common stock structure, the holders of our Class A common stock, who consist of our founders, directors, executives, employees and current holders of our convertible preferred stock (and their affiliates), will continue to be able to control the corporate matters listed above if any such matter is submitted to our stockholders for approval even if they come to own less than 50% of the outstanding shares of our common stock. Immediately after this offering, the holders of our Class A common stock, including our executive officers and directors and their affiliates, will own         % and the holders of our Class B common stock will own         % of the outstanding shares of Class A common stock and Class B common stock, combined. However, because of our dual class common stock structure these holders of our Class A common stock will have         % and holders of our Class B common stock will have         % of the total votes immediately after this offering in each of the matters identified in the list above. This concentrated control by our Class A common stockholders will limit or preclude your ability to influence those corporate matters for the foreseeable future and, as a result, we may take actions that our stockholders do not view as beneficial. The market price of our Class B common stock could be adversely affected by the structure. In addition, this may prevent or discourage unsolicited acquisition proposals or offers for our capital stock that you may feel are in your best interest as one of our stockholders. See “Principal Stockholders” and “Description of Capital Stock.”

Future transfers by holders of Class A common stock will generally result in those shares converting to Class B common stock, subject to limited exceptions, such as certain transfers effected for estate planning purposes. The conversion of Class A common stock to Class B common stock will have the effect, over time, of increasing the relative voting power of those holders of Class A common stock who retain their shares in the long term. If, for example, our executive officers (including our Chief Executive Officer), directors and their affiliates retain a significant portion of their holdings of Class A common stock for an extended period of time, they could, in the future, continue to control a majority of the combined voting power of our Class A common stock and Class B common stock with respect to each of the matters identified in the list above. For a description of the dual class structure, see “Description of Capital Stock.”

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As a new investor, you will experience immediate and substantial dilution in the book value of the shares that you purchase in this offering.

The initial public offering price is substantially higher than the pro forma net tangible book value per share of our Class B common stock immediately following this offering based on the total value of our tangible assets less our total liabilities. Therefore, if you purchase shares of our Class B common stock in this offering, which is based on the midpoint of the estimated offering price range set forth on the cover of this prospectus, you will experience immediate dilution of $        per share, the difference between the price per share you pay for our Class B common stock and its pro forma net tangible book value per share as of December 31, 2013, after giving effect to the issuance of                 shares of our Class B common stock in this offering. See “Dilution.” Furthermore, investors purchasing shares of our Class B common stock in this offering will only own approximately         % of our outstanding shares of Class A and Class B common stock (and have         % of the combined voting power of the outstanding shares of our Class A and Class B common stock in certain circumstances) after the offering even though the new investors’ aggregate investment will represent         % of the total consideration received by us in connection with all initial sales of shares of our capital stock outstanding as of December 31, 2013, after giving effect to the issuance of                 shares of our Class B common stock in this offering. To the extent outstanding options or warrants to purchase our Class A common stock are exercised, investors purchasing our Class B common stock in this offering will experience further dilution.

If securities or industry analysts do not publish research or publish inaccurate or unfavorable research about our business, our stock price and trading volume could decline.

The trading market for our Class B common stock will depend in part on the research and reports that securities or industry analysts publish about us or our business. If few securities analysts commence coverage of us, or if industry analysts cease coverage of us, the trading price for our Class B common stock would be negatively affected. If one or more of the analysts who cover us downgrade our Class B common stock or publish inaccurate or unfavorable research about our business, our Class B common stock price would likely decline. If one or more of these analysts cease coverage of us or fail to publish reports on us regularly, demand for our Class B common stock could decrease, which might cause our Class B common stock price and trading volume to decline.

We have broad discretion in the use of the net proceeds from this offering and may not use them effectively.

We cannot specify with any certainty the particular uses of the net proceeds that we will receive from this offering. We will have broad discretion in the application of the net proceeds, including working capital, possible acquisitions and other general corporate purposes, and we may spend or invest these proceeds in a way with which our stockholders disagree. The failure by our management to apply these funds effectively could adversely affect our business and financial condition, which could cause the price of our stock to decline. Pending their use, we may invest the net proceeds from this offering in a manner that does not produce income or that loses value. These investments may not yield a favorable return to our investors.

We do not intend to pay dividends for the foreseeable future.

We have never declared nor paid cash dividends on our capital stock. We currently intend to retain any future earnings to finance the operation and expansion of our business, and we do not expect to declare or pay any dividends in the foreseeable future. Consequently, stockholders must rely on sales of their Class B common stock after price appreciation, which may never occur, as the only way to realize any future gains on their investment.

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Anti-takeover provisions under Delaware law and in our restated certificate of incorporation and restated bylaws could make a merger, tender offer, or proxy contest difficult, limit attempts by our stockholders to replace or remove members of our board of directors or current management and depress the trading price of our Class B common stock.

Following the closing of this offering, our status as a Delaware corporation and the anti-takeover provisions of the Delaware General Corporation Law may discourage, delay, or prevent a change in control by prohibiting us from engaging in a business combination with an interested stockholder for a period of three years after the person becomes an interested stockholder, even if a change of control would be beneficial to our existing stockholders. See “Description of Capital Stock—Anti-Takeover Provisions—Restated Certificate of Incorporation and Restated Bylaw Provisions.”

In addition, our restated certificate of incorporation and restated bylaws that will be in effect at the closing of this offering will contain provisions that may make the acquisition of our company or changes in our board of directors or management more difficult, including the following:

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For information regarding these and other provisions, see “Description of Capital Stock.”

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