git filter-branch rewrites every commit in your repository’s history according to filters you define, which is necessary when you need to remove a large file, scrub sensitive data, or correct commit author information across all commits. As the creator of CoreUI with 25 years of open-source development experience, I’ve used this tool to purge accidentally committed credentials and remove build artifacts that bloated repository size. Note that git filter-branch is the legacy approach — git filter-repo is faster and safer for most use cases — but understanding filter-branch is still valuable for environments where installing additional tools is restricted. Both tools permanently rewrite history and require all collaborators to re-clone or re-base after the operation.