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google/diff-match-patch · source

Snapshot 0 · 2026-11-04T12:47:25Z · Python · Apache-2.0

GitHub description at capture

Diff Match Patch is a high-performance library in multiple languages that manipulates plain text.

README at capture

The Diff Match and Patch libraries offer robust algorithms to perform the
operations required for synchronizing plain text.

1. Diff:
   * Compare two blocks of plain text and efficiently return a list of differences.
   * [Diff Demo](https://neil.fraser.name/software/diff_match_patch/demos/diff.html)
2. Match:
   * Given a search string, find its best fuzzy match in a block of plain text. Weighted for both accuracy and location.
   * [Match Demo](https://neil.fraser.name/software/diff_match_patch/demos/match.html)
3. Patch:
   * Apply a list of patches onto plain text. Use best-effort to apply patch even when the underlying text doesn't match.
   * [Patch Demo](https://neil.fraser.name/software/diff_match_patch/demos/patch.html)

Originally built in 2006 to power Google Docs, this library is now available in C++, C#, Dart, Java, JavaScript, Lua, Objective C, and Python.

### Reference

* [API](https://github.com/google/diff-match-patch/wiki/API) - Common API across all languages.
* [Line or Word Diffs](https://github.com/google/diff-match-patch/wiki/Line-or-Word-Diffs) - Less detailed diffs.
* [Plain Text vs. Structured Content](https://github.com/google/diff-match-patch/wiki/Plain-Text-vs.-Structured-Content) - How to deal with data like XML.
* [Unidiff](https://github.com/google/diff-match-patch/wiki/Unidiff) - The patch serialization format.
* [Support](https://groups.google.com/forum/#!forum/diff-match-patch) - Newsgroup for developers.

### Languages
Although each language port of Diff Match Patch uses the same API, there are some language-specific notes.

* [C++](https://github.com/google/diff-match-patch/wiki/Language:-Cpp)
* [C#](https://github.com/google/diff-match-patch/wiki/Language:-C%23)
* [Dart](https://github.com/google/diff-match-patch/wiki/Language:-Dart)
* [Java](https://github.com/google/diff-match-patch/wiki/Language:-Java)
* [JavaScript](https://github.com/google/diff-match-patch/wiki/Language:-JavaScript)
* [Lua](https://github.com/google/diff-match-patch/wiki/Language:-Lua)
* [Objective-C](https://github.com/google/diff-match-patch/wiki/Language:-Objective-C)
* [Python](https://github.com/google/diff-match-patch/wiki/Language:-Python)

A standardized speed test tracks the [relative performance of diffs](https://docs.google.com/spreadsheets/d/1zpZccuBpjMZTvL1nGDMKJc7rWL_m_drF4XKOJvB27Kc/edit#gid=0) in each language.

### Algorithms
This library implements [Myer's diff algorithm](https://neil.fraser.name/writing/diff/myers.pdf) which is generally considered to be the best general-purpose diff. A layer of [pre-diff speedups and post-diff cleanups](https://neil.fraser.name/writing/diff/) surround the diff algorithm, improving both performance and output quality.

This library also implements a [Bitap matching algorithm](https://neil.fraser.name/writing/patch/bitap.ps) at the heart of a [flexible matching and patching strategy](https://neil.fraser.name/writing/patch/).