Text diff checker
Paste the original on the left and the changed version on the right. Removed lines show in red, added lines in green, unchanged lines stay dim — the same reading order a unified diff uses.
How to use
- Press Compare. By default only changed regions are shown, each with two lines of context so you can see where the edit sits.
- Untick Show only changed regions to see every line, like a full unified diff.
- Trailing whitespace counts as a difference — use Text Tools to strip blank lines first if that noise gets in the way.
How the comparison works
The tool computes a longest-common-subsequence (LCS) over whole lines, then walks the alignment to emit deletions before insertions inside each changed block — exactly the convention diff -u uses, so the output reads naturally next to real code review diffs.
Line-level (not word-level) comparison was a deliberate choice: it matches how version control and code review actually present changes, and it stays fast even for thousands of lines. Word-level diffing may come as a mode later.
Where this is handy
- Checking what a colleague actually changed in a config or response payload.
- Comparing two API responses, log excerpts or
.envfiles side by side. - Reviewing a paste of code without git history — before/after paragraphs, license texts, translations.
FAQ
How large can the inputs be?
Up to 3,000 lines per side. The LCS table for that size is about 36 MB in memory and finishes in well under a second; beyond that the page will warn you instead of freezing your tab.
Is there a character-level or word-level mode?
Not yet. Line mode covers most review workflows. If you need inline word highlighting, say so via the contact page — it is on the ideas list.
Does diffing upload my text?
No. The comparison runs entirely in your browser.