Text Diff Checker
Compare two text blocks and highlight differences line by line. Added, removed, and unchanged lines are color-coded — all in your browser, no upload, instant results.
About the Text Diff Checker
This text diff checker runs entirely in your browser. Paste two versions of text into the side-by-side boxes above and click Compare. The result shows each line color-coded: removed lines in red, added lines in green, and unchanged lines in normal color. Nothing is uploaded to a server — the comparison happens instantly with JavaScript on your device.
How the comparison works
The tool splits both inputs into lines and computes a longest common subsequence (LCS) between them. The LCS represents the lines shared by both versions in order. Lines that exist only in the original are shown as removed, lines that exist only in the modified version are shown as added, and shared lines are shown as unchanged. This produces a minimal, readable diff that highlights real changes rather than every line.
Common use cases
- Code review — Spot what changed between two snippets or revisions before merging.
- Document comparison — See edits between drafts of a text or README.
- Configuration diffs — Compare two config files to find subtle differences.
- Note taking — Track changes you made to a list or outline.
Frequently asked questions
Does this tool upload my text? No. All comparison happens locally in your browser. Your text never leaves your device.
Is the comparison case-sensitive? Yes. Lines must match exactly, including case and whitespace, to be considered unchanged.
How are empty lines handled? Empty lines are treated like any other line and participate in the comparison.
Is there a size limit? The only limit is your browser's available memory. The LCS algorithm runs in time proportional to the product of the two line counts, so very large inputs may take a moment.