AI code diff for before/after review
CheckDiffs started from a familiar frustration: vibe-coding and chat tools rewrote a whole file, and there was no clear diff — only a new wall of code. Paste the original on the left and the ChatGPT, Claude, Cursor, Lovable, or Bolt output on the right. Monaco highlights every insertion and deletion in your browser.
Nothing is uploaded for basic side-by-side. No account. Free forever for that core flow.
Open CheckDiffsWhy eyeballing an AI rewrite is not enough
Long chat or agent refactors often touch dozens of lines. Scrolling the new file misses deleted guards, swapped conditionals, and imports that moved. A side-by-side diff makes those edits obvious. CheckDiffs uses Monaco so the review feels closer to an IDE than to a static HTML highlight dump — jump between changes, merge what you accept, leave the rest.
A paste workflow that matches how you actually work
Copy the file as it was (git, editor, or the chat’s “before” block). Paste the AI rewrite into the right pane. Step through each hunk. Keep the useful renames; reject the accidental deletion. You are not looking for sixty file formats — you need a clear before/after of the code the model just wrote.
Private on purpose
AI workflows often involve real product code. Uploading that to a random compare site is a bad habit. CheckDiffs processes basic compare client-side. Details on Privacy. Who built this and why: About.
Scope — and where broader tools win
Diffchecker and similar suites go wider on formats (PDF, images) and product features. That is fine if you need that breadth. CheckDiffs stays narrow: paste-first text and code, Monaco jump/merge, private in-browser compare for AI before/after review. Prefer a feature table? Diffchecker alternative.
FAQ
Is my AI-generated code uploaded?
No. Basic compare runs in your browser with Monaco. Your before/after stays on your machine — useful when the snippet includes client code, a key you forgot to redact, or proprietary logic. Confirm in DevTools → Network if you like.
When should I use this instead of my IDE?
Use your IDE or git when the change is already a commit or a proper patch. Use CheckDiffs when you only have clipboard versions — chat spit out a full file, or a vibe builder replaced a module and you need a clear before/after before you trust it.
Does it work for long refactors?
Yes. Paste large blocks and walk change-by-change with Previous / Next. That is the point: the model rewrote half the file; you still need to see what moved, what was deleted, and what quietly changed behavior.
Do I need an account?
No. Open checkdiffs.com, paste, compare. Basic side-by-side is free forever.
Paste both sides at checkdiffs.com. Free basic side-by-side — nothing uploaded.