An Insider build refers to a pre-release version of Windows operating system software made available through the Windows Insider Program. These builds are distributed to registered testers, known as Windows Insiders, before the software is released to the general public. The main goal is to gather feedback, identify bugs, and test new features in real-world environments. Insider builds may contain experimental features and are often less stable than official releases, making them suitable for testing but not for use on production systems. Participation helps Microsoft improve security, functionality, and user experience before the final release.