From 1d4chan

In the open gaming movement, a System Reference Document (SRD) is reference for a role-playing game's mechanics licensed under the Open Game License OGL to allow other publishers to make material compatible with that game.

The first SRD was published in 2000 by Wizards of the Coast (WotC) and based upon the third edition of Dungeons and Dragons. That SRD formed the basis of WotC's various d20 systems role-playing games, including d20 Modern and d20 Future. The SRD is also the basis for role-playing games published by companies other than WotC, including Mutants and Masterminds and the Pathfinder, among others.

Some other game systems, such as FATE and the Mongoose Publishing editions of RuneQuest, have also released their own mechanics under OGL-licensed "System Reference Documents" of their own.

List of SRD for various systems[edit]