Text Diff Checker
Compare two texts side by side and see line-by-line differences highlighted in green (added) and red (removed). Uses the LCS algorithm. Browser-based.
What is the Text Diff Checker?
A text diff checker compares two versions of a text and shows what changed line by line. Added lines highlight green, removed lines highlight red, unchanged lines stay neutral. It's the same kind of view you get from git diff, but for any two blocks of text, no version control required.
How to use the Text Diff Checker
- 1
Paste the original
Drop the older or starting version of your text into the left pane.
- 2
Paste the modified version
Drop the newer or edited version into the right pane.
- 3
Click Compare
The diff appears below with line numbers from both sides, plus + and - markers. Stats at the top tally added, removed, and unchanged lines.
- 4
Swap if you got them backwards
Hit Swap to flip the panes. Useful when you realize the "original" was actually the new version.
Frequently Asked Questions
How does the diff comparison work?
Line by line, using the Longest Common Subsequence (LCS) algorithm. That's the same method behind GNU diff and git diff. The algorithm finds the minimal set of additions and removals needed to transform the original into the modified version, which keeps the diff as small and readable as possible.
Can I compare large files?
Yes. The comparison runs synchronously in your tab. LCS is O(n × m) in time, so files with tens of thousands of lines start to feel slow on lower-end devices. Files under a few thousand lines compare in milliseconds.
Is my text data private?
Both inputs and the comparison stay in your browser. Open DevTools, switch to Network, and you'll see no outbound request when you click Compare. Safe for source code, contracts, configs, or any text you wouldn't want pasted into a third-party server.