OPUS file format
Opus is the modern open codec behind voice messages and calls: outstanding quality at low bitrates, used by WhatsApp, Discord, Zoom and every WebRTC connection.
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What is OPUS?
Opus was standardised by the IETF in 2012 as RFC 6716, built from Skype's SILK speech codec and Xiph.Org's CELT. That hybrid origin is the point: it switches smoothly between speech-optimised and music-optimised modes, so one codec covers a whispered voice note and a full stereo track without changing format.
Its efficiency at low bitrates is unmatched. Speech stays clear at 24 kbps where MP3 sounds like a broken telephone, and music is decent at 96 kbps. It also encodes with very low latency, which is why real-time systems adopted it: WebRTC mandates Opus, and Discord, Zoom, WhatsApp and Telegram all use it for live audio and voice messages.
Opus is royalty-free with an open reference implementation, so anyone can ship it without licensing. The trade-off is the same one Vorbis faced: hardware players, car stereos and older software often cannot decode it. Files usually arrive as .opus or inside an .ogg container, and converting to MP3 is the standard fix for stubborn devices.
| Extension | .opus |
|---|---|
| Category | Audio |
| MIME type | audio/opus |
| Released | 2012 |
| Developed by | IETF / Xiph.Org |
| Compression | Lossy |
OPUS: frequently asked questions
- Why did I receive an .opus file?
- Almost certainly a voice message. WhatsApp, Telegram and Signal record voice notes in Opus because it keeps speech clear at tiny file sizes. Exporting the message from the app hands you the raw .opus file, which desktop music players often refuse to open.
- Is Opus better than MP3?
- Substantially, at low and medium bitrates. Opus at 96 kbps is roughly comparable to MP3 at 160 kbps, and for speech the gap is much wider. At very high bitrates both are transparent, so the advantage disappears exactly where file size stops mattering.
- Why will my music player not open Opus?
- Because the format is younger than the player. Hardware players, car stereos and older desktop software were built before Opus existed and cannot decode it. VLC and modern browsers handle it fine; for anything else, convert to MP3.
- Is Opus free to use?
- Yes. It was published as an open IETF standard with a royalty-free licence and an open-source reference implementation, deliberately so that it could be mandated in WebRTC. No fees apply to encoding, decoding or shipping it in a product.
- What bitrate should I use for Opus?
- For speech, 24-32 kbps is already clear and 64 kbps is generous. For music, 96-128 kbps is a good target and 160 kbps is close to transparent. These numbers are far lower than the MP3 equivalents, which is the whole point of the codec.
- Does converting Opus to MP3 lose quality?
- Some, because you are re-encoding lossy audio. For a voice message it is inaudible in practice. For music, encode at 256 kbps or higher so the second compression pass has room, and keep the original .opus file if you may need it again.