The WebGL working group recently announced the availability of the WebGL extension registry. The current URL is not permanent and will most likely changed. "The WebGL extension registry contains specifications for extensions to the core WebGL API. Most of these extensions are incorporated directly from the OpenGL ES or OpenGL extension registries, and refer to those extensions for their behavioral definition. Because WebGL extensions are specified as Web IDL interfaces, each specification also includes the IDL to which each implementation will comply."