Text Diff Checker
Compare two texts and see exactly what changed.
🔒 Runs entirely in your browser — nothing is uploaded.
How Text Diff Checker works
How does the text diff checker compare two blocks of text?
It splits both texts into word and whitespace tokens and runs a classic longest common subsequence algorithm, built with a dynamic-programming table, to find the longest run of tokens the two texts share in the same order. Anything outside that shared sequence gets marked as removed from the original or added in the changed version, then highlighted - green for additions, red with a strikethrough for removals.
When would I use this?
It is useful for seeing exactly what changed between two drafts of an article, a revised contract clause, or any pasted text where you want a precise word-level comparison instead of re-reading both versions side by side.
Is there a limit on how much text it can compare?
Yes - the cost of the longest-common-subsequence algorithm scales with the product of both texts' word counts, so the tool refuses to run and shows an error once that product passes 4 million, which protects your browser tab from freezing on very long documents. Like the other core tools on this site, the comparison happens entirely client-side, with nothing uploaded to a server.