The developer version of YouTube Center is an unstable version of YouTube Center, which will contain the latest features, bug fixes and etc. However, it's not guaranteed to work and could quite possibly mess up your browser, so we highly recommend taking caution when using the development build.
You can find a changelog from v2.1.7 to the developer version here.
If you find an issue, please report it on the issue tracker. However, please use the search function to make sure you don't make a duplicate.
Creating a new issue