GitHub has more than 18.6 petabytes of Git data, most of which comes from repository contents. Some of this data is junk, such as files that are no longer important, and is considered unreachable.

• Normally, GitHub doesn't remove this data, but occasionally does so to remove sensitive information.
• However, the process of removing unreachable objects from a repository's history can cause problems.
• To address this issue, GitHub has built tools to remove unreachable objects based on the last time they were written, and store them as loose objects in a cruft pack.
• Git users can trigger garbage collection and remove unreachable objects manually using the "git gc --prune" command.