Git Commit Hash Tool

What is Commit Hash?

A commit hash validator and abbreviation checker. It answers the two questions people actually have: is this hash well formed, and would git resolve this abbreviation to exactly one commit?

How it works

Each hash is checked for hexadecimal characters and length — 40 for SHA-1, 64 for SHA-256, or a 4-to-39 character abbreviation. If you paste the full hashes from git log --format=%H, the abbreviation is matched case-insensitively against them: one match is unique, several is the ambiguity git refuses to resolve, and none means the commit is not in that list. The shortest unique prefix for every hash in the list is computed the way git's own abbreviation logic does.

1. Paste or fill in the input. Drop in a commit message, a diff, a package.json, a path list or a set of options. The tool reads it locally — nothing is uploaded and no repository is contacted.
2. Adjust the rules to match your project. Every linter here takes its convention from a setting you can change: allowed commit types, header length, target branch length, known branch names. Set them once to what your team actually uses.
3. Copy the result. Generated files copy straight to the clipboard or download as a real file with the right name (.gitignore, CODEOWNERS, LICENSE, COMMIT_EDITMSG), and Reset returns every field to its default.

Examples

A commit message that fails CI

"Updated(auth): Fixed the expired-token redirect." is rejected by release automation and reported here with the exact reasons: unknown type, capitalised description, past tense and a trailing period.

A .gitignore that only half works

The Checker shows which rule decides a path — and why `!keep.txt` inside an ignored directory never fires, the mistake that sends people to Stack Overflow.

A dependency bump nobody reviewed

The package.json Diff separates added, removed and changed entries per section, so a caret bump of a runtime dependency does not hide inside a lockfile-sized pull request.

A diff pasted from a code review comment

The Diff Viewer understands several `diff --git` blocks, mode-only changes, renames and binary stubs, and calls out a pasted `--stat` summary instead of rendering an empty box.

Common mistakes

Committing a .gitignore without checking it

Rules look right and behave differently: a pattern containing a slash is anchored to the root, a trailing slash means directories only, and a file inside an ignored directory cannot be re-included. Check the paths that matter before you commit the file.

Rewriting published history

A clean commit history is worth having, but amend, rebase and filter-repo change commit hashes. Only rewrite commits that nobody has pulled; after a rewrite, push with --force-with-lease rather than --force.

Treating a generated file as if it were reviewed

These tools produce a starting point, not a decision. Check the licence text against the canonical source, read the security policy before publishing it, and make sure a CODEOWNERS team actually exists — GitHub silently ignores rules whose owner has no write access.

Putting slow checks in a pre-commit hook

A hook that takes 30 seconds gets bypassed with --no-verify within a week, and then it protects nothing. Keep pre-commit to formatting and linting, move type checks and tests to pre-push or CI.

Frequently asked questions