Git 2.51 is out, and the release continues the long process of modernizing the version control system. The update includes several technical changes, but one of the most important areas of work is Git’s move toward stronger cryptographic security through SHA-256 support.
Git has relied on SHA-1 since its creation in 2005. SHA-1 has been showing its age for years, with researchers demonstrating collision attacks that make it unsuitable for long-term use. The community has been preparing for a transition to SHA-256, but the change is not simple. Git repositories are built around object IDs, which depend on the underlying hash function. A shift in algorithms touches nearly every corner of the system.
The 2.51 release moves this effort forward. While repositories are still created with SHA-1 by default, more internal plumbing now understands and supports SHA-256. This includes parts of the transport layer and the way objects are checked and verified. Developers who are experimenting with SHA-256 repositories will find that the ecosystem is slowly catching up, making it easier to test and report issues.
The work is careful and incremental. Backward compatibility is critical since Git is used by millions of developers and in countless automated systems. Git maintainers have to balance two goals. They must strengthen the cryptographic base to keep the system secure, and they must avoid breaking existing workflows that depend on SHA-1. The result is a transition period where both algorithms are supported, giving time for tools and hosting providers to adapt.
Alongside SHA-256, the release brings other improvements. Git now handles cruft packs more efficiently, which reduces storage bloat when repositories collect unreachable objects. There are also updates to stash handling, including better support for stashing files that are outside of the index. Performance tweaks continue as well, reflecting the project’s long tradition of refining speed and scale.
For developers, the most important message in Git 2.51 is not that everything changes today, but that the foundation is being laid for the future. If you are maintaining tooling that works closely with Git objects or transport, it may be worth experimenting with SHA-256 repositories. This can help uncover edge cases before the algorithm becomes the default.
The Git project has always been about durability. Its distributed model and object store are designed to ensure data integrity, and cryptographic hashes are central to that promise. Moving from SHA-1 to SHA-256 is a necessary step to keep that integrity strong as attacks evolve.
As with any Git release, the changes come from contributions across the community. Users who want the full technical details can find them in the official release notes.