Diff Checker

Paste two versions of any text or code and instantly see what changed. Line-by-line diff with green additions, red deletions, and unchanged lines.

paste text in both panels
Original text / Version A
Changed text / Version B
Diff output ■ added   ■ removed   ■ unchanged

Frequently Asked Questions

What is a diff checker?
A diff checker compares two pieces of text (or code) and highlights what has been added, removed, or left unchanged. The name 'diff' comes from the Unix diff command, which is the foundation of version control systems like Git.
What does the + and − symbol mean?
Lines starting with + (green) appear in Version B but not Version A — they were added. Lines starting with − (red) appear in Version A but not Version B — they were removed. Lines with no symbol are identical in both versions.
Can I compare code?
Yes. Paste any code — JavaScript, Python, HTML, CSS, SQL, JSON — and the diff will highlight exactly which lines changed. This is particularly useful for reviewing changes before committing to version control.
How does the comparison algorithm work?
This tool uses the Longest Common Subsequence (LCS) algorithm — the same approach used by Git's diff engine. It finds the maximum number of lines that appear in the same order in both texts, then marks everything else as added or removed.