.opus File Extension
.opus file contains, which apps open Opus audio, how Poly supports it, and when another audio format is a better fit. File extension details for .opus
Full Support| File type | Ogg Opus audio |
|---|---|
| MIME type | |
| Encoding | Binary Ogg container with OpusHead, OpusTags, and Opus audio packets |
| Operating systems | Windows, macOS, Linux, iOS, Android |
| Opens with | VLC media player, Web browsers, FFmpeg, opus-tools |
| Poly support | Yes. Poly provides rich audio support for .opus files. |
| Indexed by Poly | Yes. Poly indexes supported tags, spoken transcripts, and audio similarity. |
| Preview in Poly | Yes. .opus files open in Poly's audio player when the browser can decode them. |
| Poly agent | Yes. The Poly agent can use the audio and its generated transcript. |
What kind of file is a .opus?
A .opus file is normally an Ogg container holding audio compressed with the Opus codec. Opus is lossy and adapts to speech, music, and low-delay interactive audio. RFC 7845 recommends the .opus suffix and audio/ogg, or the more precise audio/ogg; codecs=opus, for these files.1
The separate audio/opus MIME type formally describes framed Opus data, especially for real-time transport. Some software also uses it for .opus files, including Poly's filename mapping.
A typical file starts with the ASCII capture pattern OggS. Its first packet must contain OpusHead, followed by an OpusTags packet and the encoded audio packets.1 OggS alone is not enough to identify Opus because Ogg can carry other codecs.
.opus does not convert it. The container and audio must be encoded by a media tool.How do I open a .opus on my computer?
VLC is a straightforward cross-platform player for Windows, macOS, Linux, iOS, and Android. FFmpeg and the Xiph.Org opus-tools utilities can inspect, encode, and decode Ogg Opus files.2
Current major browsers support Opus audio, although the container matters. Chrome, Edge, Firefox, and Opera play Ogg Opus. Safari added Ogg Opus playback in version 18.4 on corresponding 2025 Apple operating-system releases.3 Older Apple software may need VLC or a converted AAC copy.
If a file fails to play, check that it is complete and actually contains Ogg Opus data. For web delivery, declare audio/ogg; codecs=opus rather than relying on the filename.
Poly support for .opus
Poly opens .opus files in its audio player, reads supported duration and tags, extracts embedded cover art, and transcribes intelligible speech. Transcript matches can jump to the relevant moment. Audio similarity helps find recordings that sound alike, and the Poly agent can use the audio and its generated transcript.
Playback still depends on the browser decoding the actual container and codec. Instrumental recordings may have little useful transcript text, while damaged or mislabeled files may not receive format-aware processing.
History of .opus
The IETF standardized the Opus codec in RFC 6716 in September 2012. It was designed to cover narrowband speech through fullband stereo music while allowing bitrate, bandwidth, and frame size to change during a stream.4
RFC 7845 standardized Opus inside Ogg in April 2016 and established .opus as the recommended filename extension.1 This container gives stored recordings checksums, timestamps, metadata, and seeking information that raw codec packets do not provide.
Working with .opus and alternatives
Opus supports bitrates from 6 to 510 kbit/s and algorithmic delay from 5 to 65.2 ms.4 RFC 7587 suggests 16 to 20 kbit/s for wideband speech, 48 to 64 kbit/s for fullband mono music, and 64 to 128 kbit/s for fullband stereo music when using 20 ms frames.5 These are starting points, not guaranteed quality levels.
| Need | Practical choice | Tradeoff |
|---|---|---|
| Calls, speech, or efficient modern delivery | Opus | Older software may not open Ogg Opus |
| Editing or a lossless working copy | WAV or FLAC | Larger files; lost Opus detail is not restored |
| Older-device compatibility | MP3 or AAC | Another lossy encode can add artifacts |
Keep a lossless master when possible. Converting .opus to WAV makes a convenient editing copy, but it cannot recover information discarded by the original Opus encoding.
Footnotes
- Internet Engineering Task Force. RFC 7845: Ogg Encapsulation for the Opus Audio Codec. ↩ ↩2 ↩3
- Xiph.Org Foundation. Opus Downloads. ↩
- MDN Web Docs. Media Container Formats. ↩
- Internet Engineering Task Force. RFC 6716: Definition of the Opus Audio Codec. ↩ ↩2
- Internet Engineering Task Force. RFC 7587: RTP Payload Format for the Opus Speech and Audio Codec. ↩