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About this tool
Turns a diff summary into a Conventional Commits prompt with type, scope, breaking-change marker and the 50/72 length rules.
The Commit Message Prompt Builder turns a diff summary into a prompt that produces a Conventional Commits v1.0.0 message with your chosen type, optional scope, breaking-change marker and the 50/72 length rules built in. It computes how many of the 50 subject characters your prefix (like feat(auth)!: ) already consumes, warns when the scope leaves too little room, and requires a real BREAKING CHANGE footer whenever you mark the change breaking.
Open Commit Message Prompt Builder on AltFTool — it loads instantly in your browser.
Paste your code or data sample into the workspace.
Pick the format, conversion, or analysis you need.
Copy the polished result straight back into your project.
The tool measures your fixed prefix against the 50-character subject convention and shows exactly how many characters remain for the description.
All eleven types — feat, fix, docs, style, refactor, perf, test, build, ci, chore, revert — follow Conventional Commits v1.0.0 and the Angular convention it references.
If your summary mixes unrelated changes, the generated prompt tells the model to write for the main one and list the rest under 'Consider splitting'.
A commit header of the form type(scope)!: description — for example feat(parser): add array support — followed by an optional body and footers, as defined by the Conventional Commits v1.0.0 specification. feat maps to a SemVer MINOR release, fix to PATCH, and a ! or BREAKING CHANGE footer to MAJOR.
Aim for 50 characters or fewer, with 72 as the practical hard cap — beyond that git log and GitHub truncate the line. Body text wraps at 72 columns. This 50/72 rule is the long-standing git convention, and the tool subtracts your type-and-scope prefix from the 50 so the model knows its real budget.
When any consumer of your public API — function signatures, endpoints, config formats, CLI flags — must change their code or usage after upgrading. Mark it with ! after the type/scope and a BREAKING CHANGE: footer describing what breaks and how to migrate; this tool refuses to build the prompt until you say what actually breaks.
Convention: a commit subject completes the sentence 'If applied, this commit will …' — so 'add rate limiting', not 'added' or 'adds'. Git's own generated messages (merges, reverts) use the imperative, and the generated prompt enforces it along with a lower-case start and no trailing period.