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JSON Diff

Last updated: 2 October 2026

Compare two JSON documents and see only what actually differs. Because the comparison is structural, reordering keys or reformatting changes nothing; the report lists each real change by its path, inside your browser.

What a structural diff sees

Both documents are parsed first, then walked together. Only differences in the data are reported: a key present on one side and not the other, a value that changed, or a value whose type changed — a number that became a string, an object that became an array. Whitespace and key order are not part of the comparison at all, because after parsing they no longer exist.

A type change is reported once, at the path where it happens, rather than being exploded into a removal and an addition for every leaf underneath. That keeps the report readable when a whole subtree changes shape.

Why this is not a line diff

A text diff — what git diff shows — compares lines. For JSON that is often misleading. Re-indenting a file, or having the same keys emitted in a different order, is normal when JSON is generated by different tools or versions of a library, and a line diff turns that into a wall of changes even though the data is identical.

The two documents below are the same document. A line diff reports four changed lines; this tool reports nothing:

{"a": 1, "b": 2}

{
  "b": 2,
  "a": 1
}

The reverse also holds, and it is the useful part: a single character changed inside a key name, or a number that moved from 3 to 4, shows up as exactly one change rather than being buried in reformatting noise.

Reading the path notation

Every change is reported at a path. $ is the document root; a dot walks into an object key, and a bracket indexes an array. So $.settings.indent is the indent key inside settings, $.features[2] is the third item of the features array, and $["weird key"] names a key that is not a simple identifier. The notation follows the same style as JSON Pointer, so a path in the report can be pasted into other JSON tooling.

What the diff cannot tell you

• Arrays are matched by position. Inserting an item at the front of a long array shifts every later element, so each is reported as changed even though the values only moved. That is a genuine limitation of any diff without a key to match on. If your items carry a stable id, sort both sides by it first, or compare a version keyed by it.
• It is not a patch. This reports differences; it does not emit a JSON Patch (RFC 6902) document and does not detect moved blocks. A value that moved appears as a removal at the old path and an addition at the new one.
• Values are compared exactly. 1 and 1.0 are the same number to the parser, but 1 and "1" are different, and a missing key is different from a key explicitly set to null.

Frequently Asked Questions