Theora

Theora is a video compression format and codec developed as part of the Ogg multimedia project by the Xiph.Org Foundation. It was designed to provide a free, patent-unencumbered alternative for digital video in the open-source ecosystem and to work with the Ogg container format. Theora's design is based on the On2 Technologies VP3 codec, and it was implemented in the reference library libtheora, which provided encoding and decoding functionality for use in media players and content pipelines.

In practice, Theora was intended for use in open video streams and streaming applications that prefer royalty-free components. It gained some adoption in early open-source video tooling and was supported by various media players that could handle Ogg Theora video streams.

However, relative to modern codecs, Theora offered modest compression efficiency and performance, and development activity declined as newer royalty-free projects—such as the Daala/AV1 track from the same ecosystem—emerged. Theora's status today is primarily historical, serving as part of the historical progression of open video codecs and the Ogg ecosystem.

The project contributed to the broader effort to provide free alternatives to patent-encumbered codecs and demonstrated the feasibility of open implementations in video encoding and streaming.