Wikidiff2

Wikidiff2 is a PHP module ('extension') that provides the external diff engine for MediaWiki. It is partly based on the original wikidiff, partly on DifferenceEngine.php. It performs word-level (space-delimited) diffs on general text, and character-level diffs on text composed of characters from the Japanese and Thai alphabets and the unified han; it includes support for Thai segmentation for word-level diffs in that language. Japanese, Chinese and Thai do not use spaces to separate words. The input is assumed to be UTF-8 encoded. Invalid UTF-8 may cause undesirable operation, such as truncation of the output, so the input should be validated by the application. The input text should have unix-style line endings.

The output is available as an HTML fragment or a JSON string.

Debian or Ubuntu
On older versions of the package you may need to run a command to actually enable the extension: (The command will be  on versions that provide PHP 5.)

If you are running a MediaWiki version older than 1.27 (newer versions automatically detect wikidiff2), add the following line to your LocalSettings.php file:

Manually
First, get and compile libthai (it should be on your OS or distro's packages).

You can download wikidiff2 through git or by downloading a tarball from https://releases.wikimedia.org/wikidiff2/.

Then compile wikidiff2. You need phpize (shipped with PHP).

Make sure that your php option is set. This is usually set in your "php.ini" file.

If you are running a MediaWiki version older than 1.27 (newer versions automatically detect wikidiff2), add the following line to your LocalSettings.php file:

HTML
The HTML diff—a number of HTML table rows with the rest of the document structure omitted—is available as a side-by-side or inline comparison. The characters "<", ">" and "&" will be HTML-escaped in the output. In the Wikidiff2 C++ library, you can access the side-by-side diff using the  class or the inline diff using the   class. Both classes include an execute method that returns the diff of the text passed in as parameters. You can also access these execute methods using the PHP wrapper functions  (for the side-by-side diff) and   (for the inline diff).

JSON
The JSON diff provides structured data to compose a visual, line-by-line comparison between two sets of text. In the Wikidiff2 C++ library, you can access the JSON diff using the  class, which includes an execute method that returns the diff of the text passed in as parameters. You can also access this execute method using the PHP wrapper function.

JSON diff schema

The JSON diff includes properties to identify changes between the two sets of text. For an example of a JSON diff, see the MediaWiki REST API compare revisions endpoint.

Links

 * Overview on the Wikidiff2 improvements by the WMDE tech team in 2017/18
 * How to release Wikidiff2 on the Wikimedia production system
 * Wikidiff2 on Phabricator