Ogg Vorbis and Opus audio formats support [Firefox and Chrome support it]
Ogg Vorbis and Opus are free and open-source audio codecs with great quality. They are developed by Xiph.Org Foundation and IETF.
Opus codec provides the best quality (latest listening tests: http://listening-test.coresv.net/results.htm for 96 kbps and http://listening-tests.hydrogenaud.io/igorc/results.html for 64 kbps) and very low latency (http://opus-codec.com/comparison/ ). More information: http://en.wikipedia.org/wiki/Opus_%28audio_format%29 . Support status: http://caniuse.com/#search=opus .
Ogg Vorbis also provides good quality. It is an old audio format and you can find many of Ogg Vorbis files in the web. Ogg Vorbis is very popular in the Linux world. More information: http://en.wikipedia.org/wiki/Vorbis and http://vorbis.com/ . Support status: http://caniuse.com/#search=ogg .
OGG, Theora and Vorbis are now supported in the Fall Creators Update by installing the Web Media Extension from the Microsoft Store: https://www.microsoft.com/store/apps/9n5tdp8vcmhs
Long-term, we expect to expand distribution of the Web Media Extension package to all Windows 10 devices so that these formats become a trusted and reliable part of the web platform available to developers.