Synacor Inc. is a technology and services company headquartered in Buffalo, New York. It provides managed portals and apps, advertising, email, authentication, and OTT video services. The company was founded in 1998 as Chek.com and changed its name to Synacor in 2001. Himesh Bhise currently serves as the CEO and William Stuart currently serves as the CFO. Beyond Buffalo, the company has offices in Boston, Dallas, London, New York City, Ottawa, Pune, San Francisco, Singapore, Tokyo, and Toronto. In 2012, Synacor became a public company (NASDAQ: SYNC) with an initial public offering (IPO) of $5.00 per share. In 2015, Synacor acquired Zimbra, an open source email, calendaring, and collaboration software suite. In the same year, Synacor acquired NimbleTV. In 2016, Synacor displaced Yahoo! as the portal provider for AT&T and was selected to provide authentication for HBO Go.

In January 1998, George Chamoun and Darren Ascone, roommates at the University of Buffalo, founded Chek.com, a Buffalo-based email infrastructure provider. It started as an affinity-branded free email provider, allowing users to create an email account at domains like Budweiser.com and Yankeesfan.net. Additionally, Chek.com provided a Business E-Communications solution, allowing companies to outsource their email hosting to Chek.com, providing an outlet for businesses to maintain email and intranet systems internally. The stated aim of the outsourced email solution was to allow smaller companies to present a professional image similar to larger, established companies.

Chek.com was an early adopter of the LAMP technology stack and was a major supporter of the growing PHP community; Chek.com (and later, Synacor) hosted php.net, the official PHP website, for a number of years prior to it being mirrored.

In 2000, Chek.com merged with MyPersonal, a San Francisco-based portal provider, to become Synacor. After the merger, Synacor started offering an extended set of products geared towards ISPs, cable companies, and telecommunications. Synacor began by hosting emails; the first such ISP was Kmart. The new agreement would provide BlueLight ISP customers with access to a 'mybluelight'-branded portal and web-based email hosted by Synacor.

In 2003, Synacor began to offer services to small and mid-size ISPs which allowed them to provide premium online content, similar to offerings by Yahoo at the time. Synacor claimed to manage complexities such as registration, rights management, and billing that customers experienced while operating their service. This technology eventually became Synacor's TV Everywhere product line. This technology also led Synacor to help shape the standards for Home-Based authentication through its long-standing participation in the Open Authentication Technology Committee (OATC) and Cable and Telecommunications Association for Marketing (CTAM). Furthermore, Synacor's TV Everywhere authentication solution helped contribute to Apple's SSO.

In 2006, during Synacor's Series C round of funding, Walden International, Advantage Capital Partners, Crystal Internet Venture Funds, Mitsui Global Investment, Rand Capital, Intel Capital, and North Atlantic Capital were investors. Synacor had originally filed an IPO in 2007 with Deutsche Bank and Bear Stearns as underwriters; however, it withdrew from filing in October 2008. A successful IPO was filed in November 2011 and priced at the beginning of 2012.