JSON Compare - Deep Diff Two Documents by Path

Input - left versus right

Left:
{
  "a": 1,
  "b": "x"
}

Right:
{
  "a": 2,
  "b": "x",
  "c": true
}

Output - path report

changed $.a
1 → 2

added $.c
true

Reviewing two versions of an API contract before a client ships

OpenAPI examples and captured responses drift. Paste yesterday's fixture on the left and today's capture on the right. Added keys are fields the client might ignore; removed keys are fields the client still reads; changed paths are the ones that break parsing. A text diff of pretty-printed JSON also works, but only after you normalize key order. This page skips that ritual.

Confirming a PATCH actually changed only the intended fields

You send {"displayName":"Ada"} and the server returns the full resource. Diff the GET-before and GET-after documents. If $.updatedAt and $.displayName changed, that is expected. If $.role changed too, the handler has a bug. The path list is the review comment.

Catching silent type changes on identifiers

Backends sometimes emit numeric ids and later switch to strings, or the reverse. A text diff may show quotes; a naive equality check in tests may coerce. This walker reports a single changed path with both previews. That is the moment to freeze the type in a schema on the JSON Schema validator rather than arguing about == in JavaScript.

Comparing pretty versus minified payloads from two environments

Staging pretty-prints. Production minifies. Staging also sorts keys alphabetically. None of that should count as a release delta. Parse both, walk both, and only ship a ticket if a value moved. If parse fails, the environment is not sending JSON - fix that on the JSON validator first.

Checking fixture drift between staging mocks and local mocks

Front-end mocks rot. Paste the MSW handler body against a real staging response. Added fields are usually safe; removed fields are usually not. Copy the path report into the PR so reviewers do not have to re-run the compare.

Reviewing feature-flag JSON without whitespace noise

Flag files are objects of objects. Teams re-indent them constantly. A tree diff answers “did anyone flip checkout.v2?” without a 200-line whitespace hunk. If the file is JSON5 with comments, convert or strip comments before this page will parse it.

Diffing translation / i18n JSON objects

Locale files are nested maps of strings. Comparing en.json to de.json lists missing keys as removed or added depending on which side is left. That is a coverage checklist, not a linguistic review. Untranslated values that still equal the English string show up as unchanged - you still need a human for that case.

Verifying a repair or editor change did not invent extra keys

After JSON repair or a tree edit, paste the original intent (if you still have a valid copy) against the new document. Heuristic repair can join values or drop comments. A path report is faster than staring at two pretty-prints.

How does JSON compare differ from a text diff?

A text diff cares about whitespace and key order. This tool parses both documents and walks the tree. {"b":1,"a":2} equals {"a":2,"b":1}. A pretty-printed file and a minified file with the same value have no diff.

What does the default sample show for $.a and $.c?

Left {"a":1,"b":"x"} versus right {"a":2,"b":"x","c":true}. Path $.a changed from 1 to 2. Path $.c was added. Path $.b is unchanged and does not appear in the report.

Are array positions treated as paths?

Yes. Arrays are compared by index. [1,2] versus [1,3] reports $[1] changed. Inserting at index 0 shifts later items and will look like many changes. That is structural comparison, not a longest-common-subsequence of array items.

Does JSON compare upload the documents?

No. Diffing runs entirely in the browser. Both drafts stay in localStorage on this device for up to 30 days and are never sent to a server.

Can I ignore a noisy path when diffing?

Not in this version. Copy the documents into the JSON editor, delete the noisy key, then compare again. There is no ignore-path checkbox and no JSON Patch output.

What about NaN, undefined, or comments?

JSON cannot represent NaN or undefined. Comments are not legal RFC 8259. If parse fails, fix syntax on the JSON validator or JSON repair first, then diff the strict documents.

Does key order count as a difference?

No. After JSON.parse, object keys are a set. Reordering keys without changing values produces an empty diff. That is the point of a tree compare versus git on minified files.

How are type changes reported?

A number 1 versus the string "1" is a single changed path, not a remove plus an add. null versus a missing key is removed or added, because object keys are a set after parse.

Can I merge the two documents after a diff?

No. This page lists added, removed, and changed paths. It is not a three-way merge and it does not emit JSON Patch. Apply edits yourself in the JSON editor.

Is this JSON diff tool free?

Yes. There is no registration, no document-size paywall, and no watermark on the path report. Compare as much JSON as your tab can hold in memory.