A .gitignore pattern tester that runs entirely in your browser. Paste a .gitignore and a file path, and see whether git would ignore that file — and the exact line and pattern that decided.

Live: https://truffle.ghostwright.dev/public/tools/gitignore/

• Tells you ignored or tracked, and points at the single rule that decided. In a .gitignore the last matching pattern wins, so a broad rule near the bottom of the file silently overrides specific rules above it.
• Handles the full matching grammar: ! re-includes a file an earlier rule excluded; a trailing slash (build/) matches directories only; a leading or mid-string slash (/dist, doc/frotz) anchors to the repo root; a pattern with no slash floats at any depth; * stops at a slash, ** crosses them, and ? matches one non-slash character.
• Models the rule almost no one knows: git never descends into an ignored directory. Once a parent like build/ is excluded, a !build/keep.txt below it can never fire — the file stays ignored and the negation is dead. The tool walks the path top-down the way git does, short-circuits the moment an ancestor directory is excluded, and flags those dead negations.
• Gives the fix for a dead negation: re-include the directory's contents with build/* plus !build/keep.txt, never build/ plus !build/keep.txt.

• A negation cannot re-include a file whose parent directory is excluded, because git does not look inside an ignored directory. Re-include the directory contents instead (build/* then !build/keep.txt).
• Trailing spaces in a pattern are ignored unless escaped with a backslash.
• A leading slash or a slash anywhere but the end anchors the pattern to the directory holding the .gitignore; otherwise it matches at any depth.

Single root .gitignore, one path at a time. It does not chain nested per-directory .gitignore files, .git/info/exclude, or the global core.excludesFile, and bracket character classes ([abc]) are matched literally rather than expanded.

node --test runs a zero-dependency regression suite. It pulls the inline engine out of index.html, runs it under Node's vm with a tiny DOM shim, and checks 22 verdict-and-deciding-rule cases against test/git-ground-truth.json — a fixture generated from the real git binary by test/regenerate-ground-truth.sh. The load-bearing case is the trap the whole tool exists for: build/ plus !build/keep.txt must report the file ignored and flag the negation as dead, which a flat per-pattern matcher gets wrong while still landing the boolean by luck.

The regenerate script documents one git footgun worth knowing: git check-ignore -v exits 0 whenever a pattern matches, even a negation, so its exit code is "did a rule match," not "is the file ignored." Take the verdict from plain git check-ignore and the deciding rule from -v.

MIT