Free diff checker for text and code
A free diff checker should do one job well: show exactly what changed between two versions. CheckDiffs is a private, in-browser tool built around Monaco’s Diff Editor — paste original and modified content, jump between changes, merge what you accept. No account for basic compare. Free forever for that core flow.
Nothing you paste is uploaded to our servers for basic compare. Open the Network tab if you want proof. Built by FT after needing a clear before/after for AI and vibe-coding rewrites — see About.
Open the free diff checkerWhat you get (and what you don’t)
You get Monaco highlighting (Plain Text, JavaScript, TypeScript, Python, JSON, HTML/CSS, SQL), change counts, Previous/Next navigation, and merge helpers without a signup wall. You do not get sixty file formats or a PDF/image suite — and we will not pretend otherwise. Search results for “free diff checker” are crowded with upgrade walls and server-side pastes; we define free narrowly: basic side-by-side stays free forever.
How people actually use it
Paste the before version on the left and the after on the right. Pick a language if you want highlighting. Walk the hunks, copy either pane, merge accepted lines into a cleaned-up left side when that helps. Common loops: reviewing ChatGPT / Claude / Cursor / Lovable / Bolt output before commit, comparing two prose drafts, or diffing JSON configs. Dedicated pages: AI code diff, text compare, JSON compare.
Privacy you can verify
Basic compare runs in the browser. We use Google Analytics for anonymous traffic stats; analytics does not receive your diff content. Full write-up on Privacy.
Vs broader compare products
If you need PDF or image compare, accounts, or share history today, a wider product (for example Diffchecker) may fit better. CheckDiffs aims to win on interactive Monaco editing, private client-side text/code compare, and an honest free tier. Feature table: Diffchecker alternative.
Pro stays TBD
Planned Pro ideas — export, ads-free experience, AI summary quota, share links / history / large-file support — are marked TBD. There is no fake Stripe button. When Pro ships, Privacy will say what data it needs.
FAQ
Is a free diff checker safe for proprietary code?
It depends on the tool. Many upload your paste to a server. CheckDiffs runs basic side-by-side in your browser with Monaco — content is not uploaded for that flow. Verify with DevTools → Network.
Will CheckDiffs stay free?
Basic side-by-side compare is free forever. Pro may later add export, ads-free polish, or an AI summary quota — TBD, no fake checkout today.
What about PDF, images, or Excel?
CheckDiffs is paste-first for text and code. Broader format suites are a better fit if you need PDF or image compare. We stay focused on interactive code/text review.
Do I need an account?
No. Open checkdiffs.com, paste, compare.
Try it at checkdiffs.com— free basic side-by-side, nothing uploaded.
About · Text compare · JSON compare · Privacy