Diff Checker
Line-by-line comparison of two blocks of text.
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About Diff Checker
Diff Checker compares two blocks of text line by line and highlights what was added and removed, using the standard longest-common-subsequence algorithm — the same approach git uses. Useful for spotting what changed between two config files, two drafts or two API responses.
How to use it
- Paste the original on the left and the changed version on the right.
- Tick "ignore whitespace" if indentation changes are noise.
- Read the highlighted result: green added, red removed.
Questions
Is there a size limit?
It caps at 2,000 lines per side. The algorithm is O(n×m), so much larger inputs would hang the page.
Does it diff within a line?
No, this is a line-level diff. A single changed character shows the whole line as removed and re-added.
Why do unrelated lines show as changed?
Usually trailing whitespace or different line endings. Turn on "ignore whitespace".
Diff Checker is free and runs entirely in your browser. No account, no upload, no watermark, no limit on use.