⚡ Instant Tools

Prompt Diff

Compare system prompts, AGENTS.md, CLAUDE.md, or Cursor rules. Live side-by-side highlights — free and private.

Privacy: Diff runs in your browser. Pair with the Prompt Linter after you settle on a version.

How to Use

  1. 1Paste the previous prompt/rules on the left and the candidate on the right.
  2. 2Use line mode for markdown files; word mode for paragraph prompts.
  3. 3Switch split vs unified depending on how you review Git diffs.
  4. 4Download the patch, then run the Prompt Linter on the final version.

Typical uses

Prompt iteration

v1 system prompt → v2 with safety + format

Catch accidental deletions of hard constraints.

Rules PR review

AGENTS.md before/after a stack change

See whether MCP or safety sections were dropped.

Tips

  • •Diff against the last shipped prompt, not a draft — fewer false changes.
  • •If similarity is high but intent changed, switch to word mode.
  • •Keep critical “never / always” lines near the top so diffs stay readable.
  • •After merging, lint the result for contradictions the diff won’t catch.

Frequently Asked Questions

What is Prompt Diff for?

It compares two versions of a system prompt, AGENTS.md, CLAUDE.md, or Cursor rules file so you can see exactly what changed before shipping agent instructions.

How is this different from the Text Diff tool?

Same Myers algorithm under the hood, but tuned for prompt/rules workflows: live diff, word or line granularity, sample prompts, patch download, and links to the Prompt Linter.

Does my prompt leave the browser?

No. Diffing runs entirely client-side.

Line vs word mode?

Line mode is best for markdown rules files. Word mode highlights smaller edits inside a line (great for long system-prompt paragraphs).

Can I download a Git-style patch?

Yes — download the unified patch and review it in PRs or commit it next to your rules.

Is it free?

Yes. No signup and no watermark.

Related Tools

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MCP Tool Checker

Score agent tool schemas

Prompt Diff

Compare system prompts and agent rules side-by-side