Text tools
Text Diff Checker
Compare two pieces of text line-by-line with a clean visual diff.
2 added1 removed2 unchanged
| 1 | 1 | The quick brown fox | |
| 2 | − | jumps over | |
| 2 | + | jumps right over | |
| 3 | 3 | the lazy dog. | |
| 4 | + | The end. |
How it works
- 1Paste the original text on the left.
- 2Paste the new text on the right.
- 3See additions in green, removals in red, and a summary count.
Use cases
- Review which lines changed between two versions of a config file.
- Spot edits a co-author made to a document.
- Compare two AI-generated answers token-difference-aware.
Frequently asked questions
Is my text uploaded?
No. The diff runs locally with a classic LCS algorithm — nothing leaves your browser.
Is this a word diff or a line diff?
Line diff. Two lines either match exactly or they don't. Identical leading whitespace counts as a match; trailing whitespace counts as a difference.
How long can the inputs be?
Up to about 5,000 lines per side. The LCS algorithm is O(n·m), so giant inputs slow down quadratically.
Read the guide
How to compare two texts line by line
A 90-second walkthrough of the diff checker — when to reach for it, how the algorithm works, and three gotchas that ruin diffs in practice.
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Remove Duplicate Lines
Strip duplicate lines from a list while preserving order.