Text Diff Checker
Compare two texts and see added, removed and unchanged lines with an LCS diff algorithm. Colors, counters and a line-by-line unified view — computed locally.
Diff appears here…
How it compares
Lines are compared with the classic Longest Common Subsequence algorithm — the same approach used by git diff for line mode. Green + lines exist only in B, red − lines only in A. Each input is capped at 2,000 lines to keep the O(n·m) matrix responsive (larger inputs are truncated and flagged).
How to use Text Diff Checker
Paste the original into the left panel and the new version into the right — differences highlight instantly, character by character, with insertions and deletions color-coded in place. Options let you ignore case and whitespace noise so formatting churn does not drown the real change.
The diff is deliberately conservative: it finds edits rather than guessing moves, which keeps output readable for prose, config changes, JSON payloads and code samples alike. Run a formatter before diffing generated files — formatting first makes the semantic delta obvious.
Frequently asked questions
How accurate is the comparison?
A line-level longest-common-subsequence diff (the approach git uses) aligns both texts and marks additions, deletions and unchanged blocks, with character highlighting inside changed lines.
Can I ignore whitespace or case?
Yes. Options fold capitalization and ignore indent-only changes, which keeps the diff focused on real content edits instead of formatting noise.
Is there a size limit?
Large documents work, though the browser spends time proportional to text size. For megabyte files, diffing the interesting range first is noticeably faster.
Are my two texts uploaded anywhere?
No. All comparison logic runs locally in the tab, so diffing confidential documents, configs or credentials sends nothing anywhere.