diff-patch is a library that exposes two functions, diff and patch.

The library does not have any dependencies.

The diff function takes two objects (obj1 and obj2) and deep compares them, returning an object that represents the difference between the two (the diffData). diffData is an object that can be used to apply the diff to obj1 to get an object that is the same as obj2.

The patch function takes an obj and a diffData object and applies the diff to the object, returning a new object.

The diff and patch functions are implemented in the following languages:

  • TypeScript
  • Python3
  • Dart (experimental)

The diffData object can be used interchangeably between the languages.
This makes this library very useful for networked applications, where the client and server are written in different languages.

diffData can be serialized to JSON and deserialized back to an object. It aims to be as small as possible, and is designed to be used in a networked environment.

More languages will be added in the future, contributions are welcome.



To install the Dart version of diff-patch, run:

dart pub add fsoft_diff_patch

Then, in your Dart code:

import 'package:fsoft_diff_patch/fsoft_diff_patch.dart';

void main() {
  final a = {
    "a": 1,
    "b": 2,
    "c": {
      "d": 3,
      "e": 4,
      "f": {
        "g": 5,
        "h": 6,
  final b = {
    "a": 1,
    // "b": 2, // b is deleted
    "c": {
      "d": 9, // d is changed
      "e": 4,
      "f": {
        "g": 5,
        "h": 7, // h is changed
        "i": 10, // i is added
  // diff a and b and create a diffData object
  final diffData = diff(a, b);
  // print diffData in the console
  print("DIFF DATA\n${json.encode(diffData)}");
  // apply diffData to a and create a new object
  final patched_a = patch(a, diffData);
  // print patched_a in the console
  print("\n\nPATCHED OBJ\n${json.encode(patched_a)}");
  // check if patched_a is equal to b
  print("\n\nSAME OBJECT: ${json.encode(patched_a) == json.encode(b)}");


This library was created by Fabio Rotondo.

New language implementations are more than welcome.
Please open an issue or a pull request if you want to contribute.


The official repository for this library is here.


This library is licensed under the MIT License.
See the LICENSE file for details.