API contracts
Compare a documented response with a live one to catch renamed or removed fields before they break a client.
JSON diff
JSON diff checker for files and API responses
Compare two JSON documents key by key. Useful for API contract changes, feature flags, translation files and environment configuration.
Original JSON
New JSON
Everything is compared in your browser. No text or file ever leaves this device.
Paste your original text on the left, the revised version on the right, then press Compare.
Config and flags
Diff two settings files to see which flag differs between environments without scrolling through both.
Translation files
Find missing or reworded locale strings between two language bundles at a glance.
Frequently asked questions
- How do I diff two JSON files online?
- Paste each JSON document into a pane or upload two .json files, then press Compare. Redline shows added, removed and changed keys line by line.
- Does it handle minified JSON?
- Format both sides first — a single-line document diffs as one line. Character granularity still pinpoints the change if you can't reformat.
- Can I compare API responses?
- Yes. Paste two responses to spot a changed field, a dropped key or a type change between environments or releases.
- Are keys compared in order?
- Redline is a text diff, so key order matters. Sort or format both documents the same way for the cleanest result.