Text Diff Checker

Compare two texts and see exactly what changed — line by line. Runs entirely in your browser.

How Line-by-Line Diff Works

The diff algorithm compares two texts line by line. Lines that appear in both are shown as unchanged. Lines that appear only in the original are marked as removed. Lines that appear only in the modified version are marked as added.

This tool uses a longest-common-subsequence (LCS) approach — the same algorithm behind git diff and diff on Unix systems.

Common Uses

• Comparing code versions before committing
• Spotting differences between two configuration files
• Reviewing edits between document drafts
• Checking API response changes

Frequently Asked Questions

Can I compare files instead of pasting?

Not in this tool — copy the contents of each file and paste them into the two boxes. Future versions may support file upload.

Why does it show unchanged lines too?

Context. Seeing unchanged lines around a change helps you understand where the change happened. It's the same reason git diff shows surrounding context.

Do you log my text?

No. The comparison runs entirely in your browser. Nothing is sent to our servers.