JSON Diff
Compare two JSON documents and see exactly what changed — added, removed and modified.
Quick answer: JSON Diff: compare two JSON documents and see exactly what changed — added, removed and modified. Runs entirely in your browser, free, no signup.
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The dotted-path annotation is what makes this more useful than a plain text diff. When the tool reports a change at $.user.address.postcode, you can jump straight to that node in a large document instead of scanning line by line — invaluable when you are comparing two API responses that differ in one buried field, or checking that a config migration touched only what you intended.
Remember the two comparison rules, because they trip people up. Object keys are matched by name, so reordering keys produces no diff — semantically correct, since JSON objects are unordered. Arrays, however, are compared positionally: inserting an element at the front shifts every index and can light up the whole array as changed. When array order is not meaningful in your data, sort both sides first (for example with sort lines on a flattened list) so the diff reflects real content changes.
A subtle gotcha is number formatting. JSON 1.0 and 1 parse to the same numeric value and won't diff, but a value stored as the string "1" is a genuine type change from the number 1 — exactly the kind of contract drift that breaks a strict consumer. The diff surfaces these because it compares parsed values, not raw text.
Since everything is parsed and compared locally, it is safe for confidential payloads, and the output copies cleanly into a pull-request comment or a change report when you need a reviewer to see precisely what moved.
Frequently asked questions
- How does it handle key ordering?
- Keys are compared by name, not position — two objects with the same keys in different orders are equal.
- What about array order?
- Arrays are compared positionally — the diff treats them as ordered. If you want set semantics, sort both arrays first.
- Will huge JSON documents be slow?
- The diff is O(n) over the smaller of the two trees, so multi-megabyte documents finish in well under a second.
- Are my JSON files uploaded?
- No — comparison runs entirely in your browser. Even confidential JSON is safe to paste here.
- Can I export the diff?
- Yes — copy the diff lines or download as JSON for use in a code review or change report.