Visual diffs/yue

A visual diff compares and shows differences between rendered (or displayed) documents, as opposed to showing the text (or markup) that is used to format such documents. There are several "visual diff" efforts in the MediaWiki world:


 * The most visible one is a visual diffs system inside the visual editor, comparing the HTML of two documents (released in March 2017; pictured); eventually, this will be available on MediaWiki history and diff pages too.
 * As part of their testing efforts, the Parsing team created the "Visual Diff Testing" tool (released around April 2016), which is a pixel differ of the page rendered as an image, used to identify differences between Parsoid and the legacy parser.
 * Extension:On-Article Diff Highlighting (2011)
 * As part of Google Summer of Code 2008, guyvdb mentored by Brion created an HTML diffing tool in MediaWiki core, which was later removed in 2009.