Use of Ogg formats in HTML5

The HTML5 draft specification adds video and audio elements for embedding video and audio in HTML documents. The specification had formerly recommended support for playback of Theora video and Vorbis audio encapsulated in Ogg containers to provide for easier distribution of audio and video over the internet by using open standards, but the recommendation was soon after dropped.

Because some visitors and publishers choose not to take part in the use of proprietary software, web content has been made available through freely implementable open standards in order to reach these users. As multimedia is already mainstream on the web through proprietary data formats (such as Windows Media Video and MP4) and browser plugins (such as Adobe Flash Player), developers had hoped Theora and Vorbis would become part of the HTML5 specification.

Users affiliated with the free software movement claimed the following advantages:

CTO at Opera Software, Håkon Wium Lie explained in a Google tech talk entitled "The <video> element" the proposal of Theora as the video format for HTML5:

I believe very strongly, that we need to agree on some kind of baseline video format if [the video element] is going to succeed. [...] We want a freely implementable open standard to hold the content we put out. That's why we developed the PNG image format. [...] PNG [...] came late to the party. Therefore I think it's important that from the beginning we think about this.

...
Wikipedia