what is cumulative update preview

A cumulative update preview is a non-security update that includes changes that will be included in the next Patch Tuesday update. These updates are usually released towards the end of the month and are optional, meaning they are not installed automatically. Preview updates may introduce new features, fix bugs and issues, or make changes to existing features. They are essentially beta versions of the regular cumulative updates. Preview updates do not include security patches for Windows. Admins can test upcoming fixes released in the preview updates before they are broadly released. It is best to wait for the regular patch Tuesday updates, which will contain the code in those preview updates, but possibly a more stable version, because many users have difficulties after manually installing a preview update.