Lee Daniel Crocker (born July 3, 1963) is an American computer programmer.

This software, originally known as "Phase III", went live in July 2002 and became the foundation of what is now called MediaWiki.

He is a co-author of the PNG specification, and was also involved in the creation of the GIF and JPEG image file formats.

He invented the per-scanline variable pre-filtering compression method used by PNG, the sum-of-abs heuristic used by many encoding programs.

[3] In June 2010, Crocker was among those recognized by the Software Tools Users Group (STUG) as a major contributor to MediaWiki when they awarded MediaWiki and the Wikimedia Foundation the USENIX Advanced Computing Technical Association STUG award for "the largest collaboratively edited reference projects in the world, including Wikipedia".