Generate a diff between two JSON strings.


Here's a basic example which features a deleted object, a new object, a changed object, and a deeply changed object:

import 'package:json_diff/json_diff.dart';

final left = {"a": 2, "b": 3, "c": 5, "d": {"x": 4, "y": 8}};
final right = {"b": 7, "c": 5, "d": {"x": 4, "z": 16}, "e": 11};
final differ = JsonDiffer.fromJson(left, right);
DiffNode diff = differ.diff();
print(diff.added);              // => {"e": 11}
print(diff.removed);            // => {"a": 2}
print(diff.changed);            // => {"b": [3, 7]}
print(diff.node);               // => a Map<String,DiffNode>
print(diff.node['d']);          // => a DiffNode
print(diff.node['d'].added);    // => {"z": 16}
print(diff.node['d'].removed);  // => {"y": 8}

So that's pretty fun. So when you diff two JSON strings, you get back a DiffNode. A DiffNode is a heirarchical structure that vaguely mirrors the structure of the input JSON strings. In this example, the top-level DiffNode we got back has

  • an added property, which is a Map of top-level properties that were not found in left, and were found in right.
  • a removed property, which is a Map of top-level properties that were found in left, but were not found in right.
  • a changed property, which is a Map of top-level properties whose values are different in left and in right. The values in this Map are two-element Arrays. The 0th element is the old value (from left), and the 1st element is the new value (from right).
  • a moved property, which is a Map of indexes, where key is the original index of an element, and value is index in the changed list.
  • a node property, a Map of the properties found in both left and right that have deep differences. The values of this Map are more DiffNodes.
  • a path property, which is a List of indexes, describing the path from the root where this DiffNode is operating.


Contributions welcome! Please read the contribution guidelines.


This is not an official Google product.


A library for determining the difference between two JSON objects. [...]