google-diff-match-patch 0

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Diff, Match and Patch Library Neil Fraser

This library is currently available in seven different ports, all using the same API. Every version includes a full set of unit tests.


C++: * Ported by Mike Slemmer. * Currently requires the Qt library.

C#: * Ported by Matthaeus G. Chajdas.

Dart: * The Dart language is still growing and evolving, so this port is only as stable as the underlying language.

Java: * Included is both the source and a Maven package.

JavaScript: * diff_match_patch_uncompressed.js is the human-readable version. Users of node.js should ‘require’ this uncompressed version since the compressed version is not guaranteed to work outside of a web browser. * diff_match_patch.js has been compressed using Google’s internal JavaScript compressor. Non-Google hackers who wish to recompress the source can use:

Lua: * Ported by Duncan Cross. * Does not support line-mode speedup.

Objective C: * Ported by Jan Weiss. * Includes speed test (this is a separate bundle for other languages).

Python: * Two versions, one for Python 2.x, the other for Python 3.x. * Runs 10x faster under PyPy than CPython.

Demos: * Separate demos for Diff, Match and Patch in JavaScript.

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


  • Compare two blocks of plain text and efficiently return a list of differences.
  • Diff Demo


  • Given a search string, find its best fuzzy match in a block of plain text. Weighted for both accuracy and location.
  • Match Demo


  • Apply a list of patches onto plain text. Use best-effort to apply patch even when the underlying text doesn't match.
  • Patch Demo

Currently available in Java, JavaScript, Dart, C++, C#, Objective C, Lua and Python. Regardless of language, each library features the same API and the same functionality. All versions also have comprehensive test harnesses.


This library implements Myer's diff algorithm which is generally considered to be the best general-purpose diff. A layer of pre-diff speedups and post-diff cleanups surround the diff algorithm, improving both performance and output quality.

This library also implements a Bitap matching algorithm at the heart of a flexible matching and patching strategy.

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