JSON Diff

Produce a minimal deterministic RFC 6902-style add/remove/replace patch turning one JSON document into another.

Description

Compare two JSON documents and generate a deterministic add, remove, and replace patch.

JSON diff turns two serialized JSON values into a compact machine-readable description of their differences. It is useful for API regression fixtures, configuration reviews, and producing a patch that can be passed directly to the JSON Patch applier.^{[1, 2]}

When to use JSON Diff

Compare before-and-after API responses
Create a replayable change set for JSON fixtures
Locate nested object and array differences with JSON Pointer paths

How the calculation works

Objects are compared by sorted keys, arrays are compared positionally, and scalar or type changes produce `replace`. Removed trailing array items are emitted from the highest index downward so later indices remain valid. Paths escape `/` and `~` according to JSON Pointer.^{[1, 2]}

Interpreting the result

`opCount` gives the patch length and `patch` contains compact JSON. An empty array means the parsed documents are structurally equal. The generated operations are deterministic and round-trip through the companion applier, but they are not guaranteed to be the globally shortest possible edit script.

Important limitations

Array items are matched by position rather than by identity or key.
Different object key order is ignored because JSON objects are compared structurally.
The output uses only add, remove, and replace operations.

References

RFC 6902: JavaScript Object Notation (JSON) Patch — RFC Editor
RFC 6901: JavaScript Object Notation (JSON) Pointer — RFC Editor