Text Diff Checker
Compare two texts and see the differences
Quick steps
Paste both versions
Drop the original on the left, the changed version on the right.
Read the diff
Green lines were added, red lines were removed. Line numbers on both sides match the original positions.
Adjust comparison
Toggle 'Ignore case' or 'Ignore whitespace' for forgiving comparisons.
Frequently asked questions
How does the diff work?
We use a classic longest common subsequence (LCS) algorithm to find the minimum number of additions and removals that transform the original into the changed text.
Does it diff within lines?
No, this is a line-level diff. For character-level diffs within changed lines, dedicated tools like diff-match-patch are better.
Is my text uploaded?
No. The diff is computed entirely in your browser.
Can I diff very large files?
The LCS algorithm is O(n*m) in time and memory. Texts under 10,000 lines each are fast; much larger files may freeze the page briefly.