Diff Checker
Compare two blocks of text, code or JSON and see exactly what changed — added, removed and unchanged lines, highlighted live as you type.
Differences
What Diff Checker does
Live comparison
The diff updates as you type in either pane — no button to press.
JSON-aware
Compare JSON by structure so formatting differences don't create noise.
Line-accurate
An LCS algorithm marks exactly which lines were added or removed.
100% local
Your text never leaves your browser.
Frequently asked questions
How does the diff checker work?
Paste two versions of your text into the left and right panes. The tool computes a line-by-line difference using a longest-common-subsequence algorithm and highlights added, removed and unchanged lines instantly as you type.
Can I compare JSON regardless of formatting?
Yes. Enable Compare as JSON and both sides are pretty-printed with sorted structure before diffing, so two JSON documents that are structurally equal but formatted differently show as identical.
Is my data sent anywhere?
No. The entire comparison runs locally in your browser with JavaScript. Nothing you paste is uploaded.
What can I compare?
Anything text-based: code, configuration files, API responses, JSON, logs, prose — any two blocks of text where you want to see what changed.
Last updated 2026-08-08