Gmail is a free, advertising-supported email service developed by Google. Users can access Gmail on the web and through mobile apps for Android and iOS, as well as through third-party programs that synchronize email content through POP or IMAP protocols. Gmail started as a limited beta release on April 1, 2004, and ended its testing phase on July 7, 2009.
At launch, Gmail had an initial storage capacity offer of 1 gigabyte per user, a significantly higher amount than competitors offered at the time. Today, the service comes with 15 gigabytes of free storage. Users can receive emails up to 50 megabytes in size, including attachments, while they can send emails up to 25 megabytes. In order to send larger files, users can insert files from Google Drive into the message. Gmail has a search-oriented interface and a "conversation view" similar to an Internet forum. The service is notable among website developers for its pioneering use of Ajax.
Google's mail servers automatically scan emails for multiple purposes, including to filter spam and malware, and to add context-sensitive advertisements next to emails. This advertising practice has been significantly criticized by privacy advocates due to concerns over unlimited data retention, ease of monitoring by third parties, users of other email providers not having agreed to the policy upon sending emails to Gmail addresses, and the potential for Google to change its policies to further decrease privacy by combining information with other Google data usage. The company has been the subject of lawsuits concerning the issues. Google has stated that email users must "necessarily expect" their emails to be subject to automated processing, and claims that the service refrains from displaying ads next to potentially sensitive messages, such as those mentioning race, religion, sexual orientation, health, or financial statements. In June 2017, Google announced the upcoming end to the use of contextual Gmail content for advertising purposes, relying instead on data gathered from use of its other services.
As of February 2016, Gmail has one billion active users worldwide, and was the first app on the Google Play Store to hit one billion installations on Android devices. According to a 2014 estimate, 60% of mid-sized US companies, and 92% of startups, were using Gmail.