Paste two versions of a text, code or list and see exactly what changed — added, removed and edited lines, with the changed words highlighted. Nothing is uploaded.
🔒 This tool runs entirely in your browser. Nothing you enter or upload is sent to our servers.
How to use the Diff Checker
- Paste the original text in the left box and the changed text in the right box, or drop a file onto either box.
- The comparison appears below as you type. Removed lines are red, added lines are green, and within an edited line the exact words that changed are highlighted.
- Switch between side-by-side and inline views, and tick Ignore case or Ignore whitespace to hide differences that don’t matter.
- Copy or download the result as a standard unified .diff file if you need to share or apply it.
About this tool
Comparing two versions by eye is unreliable: a changed digit in a contract, a missing line in a config file or a reordered paragraph is easy to miss. A diff checker lines the two texts up and marks every difference, so you can review a change in seconds — an edited document against the original, two versions of a script, a list exported from two systems, or what an AI rewrite actually changed.
The comparison works line by line using the Myers diff algorithm, the same approach used by Git, so the result is the smallest set of added and removed lines that turns the first text into the second. Where a line was edited rather than replaced, the changed words inside it are highlighted too. Long stretches of unchanged lines are folded so the changes stand out; click a fold to show what is inside it.
Both texts stay in your browser. Nothing is uploaded or saved, which matters when the thing you are comparing is a contract, source code or customer data. The download is a standard unified diff, the format that git diff and diff -u produce, so it can be read by code review tools or applied with patch.
Frequently asked questions
How do I compare two texts?
Paste the original on the left and the new version on the right. Differences appear immediately below: red lines were removed, green lines were added, and an edited line shows both versions with the changed words highlighted.
Can I ignore spaces or capital letters?
Yes. Ignore whitespace treats lines as equal when they differ only in spaces, tabs or indentation, and Ignore case treats “Hello” and “hello” as the same. The original text is still displayed exactly as entered.
Can I compare code?
Yes. The comparison is plain text, so it works for any programming language, JSON, CSV, HTML or config files. Use the inline view and download the .diff file to share the change.
Is my text uploaded or saved?
No. The comparison runs entirely in your browser, and nothing is sent to a server or stored. Closing the page discards both texts.
Can I compare Word or PDF files?
Not directly — paste their text in. To get the text out of a PDF, use our PDF to Text tool, then paste it here.
Is there a size limit?
There is no fixed limit, but very large texts that differ almost everywhere take longer to compare. Tens of thousands of lines with ordinary edits compare in well under a second.