I'm currently working on a website which has to stream audio files. Since bandwidth is always an issue, the file size should be as small as possible. I wonder what audio formats I should provide.

  • MP3 - Most common format but low quality, I don't know if it's even required, since AAC is well supported by the browsers incapable of playing free codecs
  • MP4 AAC - Nice quality / small filesize, supported by Safari / Mobile Devices / IE9 / Flash / Chrome
  • A free codec - well, until recently, there only was Ogg Vorbis, but Ogg Opus is standardized now and it's really good!


  • Is it time yet to use Opus instead if Vorbis? Firefox supports Opus since version 15, and Opera has support on its roadmap - I guess Chrome will follow in the future too.

  • Do I still have to provide an MP3 file?


Speaking more as a potential user of your site than as a webmaster, I'd say stick with MP3 for now, for two reasons.

First, unless you're expecting to serve only geeks who aren't put off by words like codec, or you're sure all of your visitors will be using the latest and greatest browsers, I think it's better to ensure that for the average visitor, things will Just Work.

Second, my sense is that MP3 quality (of sufficient kbps) is fine for people listening with computer speakers or earbuds. You can always provide download links to superior quality options. For the audiofiles. ;)

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If you target only HTML5 you cand go safely without MP3, but if you want also backward compatibility you may need it.

MP4 AAC is the best choice. You can go also with WebM format to cover what is not covered by MP4 AAC.

OGG Opus is still not supported on other browser than Firefox bu it will probably be, since everyone wants to follow the standard.

Of course nothing beet in support and quality WAV format, but then the size matters if the bandwidth is a problem.

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