Diff Checker
Compare two texts side by side and find differences. Support for character, word, and line comparison.
What is a Diff?
A diff (short for "difference") is a representation of the changes between two texts — typically the lines added, removed, or modified to turn one into the other. The format originated with the Unix
diff command in 1974 and is now central to source control: git diff in code review, GitHub PR views, IDE merge tools, and rsync all use diff algorithms. Modern diffs support multiple granularities: line-level (best for code), word-level (best for prose), and character-level (best for short strings). The dominant algorithm is Eugene Myers's 1986 longest common subsequence solution, which finds the shortest edit script in O(ND) time. This checker computes diffs locally in your browser. Cleaning text before comparison? Use the Text Formatter; need to swap one pattern across both sides? Try the Find & Replace tool.Original Text
Modified Text
Diff Mode
Ignore case
Ignore whitespace
How to use this tool
- 1Paste original and changed textDrop the two versions into the left and right panes. Order matters — left is treated as the 'before' baseline.
- 2Pick a granularityChoose line for code, word for prose, or character for short strings. Switch between views to spot different patterns.
- 3Read the highlighted diffGreen = inserted, red = deleted, yellow = changed. Sync-scroll keeps both panes aligned as you review.