Sample Opus audio files for testing — free, CC0, hotlinkable

Opus is the royalty-free audio codec the IETF standardised in RFC 6716, and the one browsers, WebRTC and voice applications settled on. A .opus file is Opus inside an Ogg container, as RFC 7845 specifies.

opus/30s.opus is a 440 Hz sine wave, thirty seconds long, stereo, encoded at 96 kbps. The same kind of tone appears across the other audio formats here, so one pipeline can be compared across codecs.

One gotcha is built into the format: Opus decoders produce 48 kHz output, and tools report 48 kHz whatever rate the source had. The original rate survives only as an informational header field. Code that expects the source rate back, or that assumes 44.1 kHz, gets this file wrong in a way a quick listen will not reveal.

Use it to test browser playback, transcoders, waveform renderers, audio upload forms and handling of the audio/opus media type. It is also a check that code reads the codec from the stream: an Ogg file can carry Opus, Vorbis or FLAC. Related formats: Ogg Vorbis, MP3 and M4A.

curl -O https://loremfile.dev/opus/30s.opus

<audio src="https://loremfile.dev/opus/30s.opus" controls></audio>