Windows Insider Program

Windows Insider Program is a software testing program by Microsoft for Windows 10 and Windows Server. The user can opt in the program to test out new features and new versions of the operating system that were previously only accessible to developers. The first build that was released from the Insider Program was 9841. In addition, more builds are also released to other platforms and in different formats.

Channels
The Insider program allows users to pick the builds they want to receive by enrolling to a specific channel. The Insider infrastructure is also used for Microsoft's internal selfhosting effort, with internal channels receiving builds before the public channels or delayed compared to the public channels, however, they are not a formal part of the Insider program.
 * Dev Channel (formerly Fast Ring): This is the first channel in the Insider program to receive builds from the current development cycle. Between 2017 and 2019 an option called Skip Ahead also existed, which allowed a limited number of users to receive builds from the next development cycle, while the rest received builds from the stabilization stage of the current cycle.
 * Beta Channel (formerly Slow Ring): This channel receives builds of the next Windows 10 feature update. If both Dev and Beta channels track the same development cycle, the Beta channel gets the same builds after being tested in the Dev channel.
 * Release Preview Channel: This channel receives new app and OS updates (including feature updates) prior to their general rollout to consumers. It is the youngest Insider channel, being introduced in 2016.