Diff Checker
Compare two texts and highlight every added and removed line.
How the diff algorithm works
The diff is computed using the Longest Common Subsequence (LCS) algorithm — the same technique underlying git diffand most professional diff tools. LCS finds the largest set of lines that appear in both texts in the same order. Lines in the original that aren't in the LCS are marked red (removed), and lines in the modified text that aren't in the LCS are marked green (added). Unchanged lines are shown in neutral colour.
Frequently asked questions
Does this work for code diffs?
Yes. Paste any code into both panes — the diff is purely text-based and works with any programming language, markup, or config file. For syntax highlighting on top of diffs, use a full IDE or GitHub's diff view.
Is the comparison case-sensitive?
Yes. "Hello" and "hello" are treated as different lines. This matches the behaviour of standard diff tools and is important for code where case matters.
Is my text sent to a server?
No. The entire diff is computed in your browser. Your text never leaves your device, making it safe to use with private documents, proprietary code, or sensitive configuration files.
