Diff Checker
Compare two texts side-by-side and see additions, deletions, and changes highlighted.
Original
Modified
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Get Early AccessHow diff algorithms work (what you see in the output)
Our diff checker uses the Myers algorithm — the same one that powers git diff, diff on Unix, and most IDE comparison tools. It finds the shortest edit script (sequence of inserts and deletes) that transforms the original text into the new text.
Color key in the output:
- Green lines — present in the new version, not the original (insertion).
- Red lines — present in the original, removed in the new version (deletion).
- Yellow highlight within a line — the line exists in both, but specific words changed (intra-line diff).
- Unchanged lines — shown faded as context, to orient the reader.
For structural diffs (e.g. "which JSON keys changed?"), first run both sides through our JSON Formatter to normalize whitespace and sort keys — then a line diff becomes a semantic diff.
Common use cases
- Code review without a PR — paste old and new file content to see changes before committing.
- Compare API responses — fire the same request from two environments, diff the JSON.
- Config file changes — see exactly what changed in
nginx.confbefore applying. - Contract / legal text revisions — show what a counterparty changed in a redlined version.
- Translation QA — diff the source file against the translated file to spot untranslated strings.
- Log comparison — diff two test runs to find the one new error line.
Frequently Asked Questions
How do I compare two text files or code snippets online?
Paste the original text on the left and the new text on the right. The diff checker highlights additions, deletions and modifications line-by-line — green for inserts, red for deletes. Works for source code, JSON, configs, contracts or any plain text.
Is this a free diff checker without signup?
Yes. Fully client-side — your text never leaves the browser. No signup, no character limit, no paywall. Ideal for code reviews, comparing API responses, or checking what changed in a config file.
Can I diff JSON, YAML or XML structurally?
The tool performs a line-based diff (like `git diff`). For structural JSON diff, format both sides first with our JSON Formatter to sort keys and normalise indentation, then paste them in. That turns a line diff into a semantic diff.
How is this different from `diff` on Linux or `git diff`?
It's the same Myers diff algorithm that powers `git diff` and Unix `diff`, but rendered in a side-by-side browser UI with syntax highlighting, word-level change detection and copy-to-clipboard. No terminal needed.
Can I share a diff with a teammate?
Small diffs (under ~1000 lines) are URL-encoded into the page hash, so you can bookmark or share the link. Large diffs — copy the output manually or screenshot. All text stays on your device.
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