Text Diff Checker
Paste an original and a revised version to see added, removed, and unchanged lines in one clear diff. Useful for copy reviews, configuration checks, and quick version comparisons.
Compare two blocks of text line by line and highlight unchanged, added, and removed lines. The comparison uses a longest-common-subsequence matrix so matching line order can be preserved in the result.
How to compare two text versions
- Paste the original text on the left.
- Paste the changed text on the right.
- Press Compare.
- Review lines marked as added, removed, or unchanged.
- If the input is too large for the matrix limit, reduce the compared text and try again.
Line-based LCS comparison
Line endings are normalized before comparison, and the algorithm compares complete lines rather than individual characters or words. Added and removed entries are derived from a longest-common-subsequence table.
To avoid excessive memory use, the tool refuses comparisons when left-line count multiplied by right-line count exceeds 400,000 matrix cells. It reports the number of changed line entries, not an edit distance in characters.
Privacy and limitations
The comparison runs locally in the browser and the pasted text is not intentionally sent to a server. This is a line-oriented diff, so a small edit inside one line is shown as one removed line and one added line rather than as a character-level highlight.
Frequently asked questions
Is this a character-by-character diff?
No. It compares whole lines.
Are Windows line endings supported?
Yes. CRLF and CR are normalized to LF before comparison.
Why can a large comparison be rejected?
The LCS matrix is capped at 400,000 line-pair cells to limit memory and processing cost.
Are identical lines shown?
Yes. Unchanged lines remain in the result with a neutral marker.
What does the changed count represent?
It counts added and removed line entries.