What is the OPUS file format?
Files with the .opus extension contain audio - music tracks or human speech - compressed with a lossy method. For compression, both the SILK algorithm and an algorithm based on the MDCT transform called CELT are used, providing a high level of flexibility and low complexity that enables the format to encode sound in real-time, even on relatively modest processors.
A unique feature of sounds stored in .opus files is that their parameters can differ in each fragment (a so-called "frame", covering 20 ms by default):
- Bitrate - from 6 kbps up to 510 kbps
- Bandwidth
- Complexity
- Algorithm type (SILK, CELT, or a hybrid blend of both)
The .opus format is an open standard defined by the IETF (Internet Engineering Task Force), created by the Xiph.Org Foundation in collaboration with Skype Technologies (now part of Microsoft). The reference implementation is contained within libopus, available under the New BSD licence. Sound in this format can be stored at one of five internal bandwidths (narrowband through fullband, up to 48 kHz) and supports up to 255 channels in multi-stream mode. It was designed to be used within file containers, most commonly an OGG file, and is also widely used for real-time voice communication on the web via WebRTC. Modern browsers natively decode .opus in both Ogg and WebM containers.
Security & safety
RISK: LOWAn .opus file is plain compressed audio - it contains no executable code, so the format itself is safe. Standard caveats only: malformed media files can target player vulnerabilities (keep VLC/players updated), and voice messages can carry sensitive personal content - mind what you upload to online converters.
Format details
in a nutshellFULL NAMEOpus Audio File (Ogg Opus)
DEVELOPERXiph.Org Foundation / IETFsince 2012 (codec standardized as RFC 6716, September 2012; Ogg encapsulation RFC 7845, 2016)
CATEGORYAudio Files
MIME TYPEaudio/ogg (codecs=opus); audio/opus is the RTP/streaming registration
TYPElossy compressed audio - Opus codec in an Ogg container
STANDARDOpen · royalty-free
MAGIC BYTES · FILE SIGNATURE
OFFSET
00010203
HEX
4F676753
ASCII
OggS
The string "OpusHead" appears at offset 28 (start of the first Ogg page payload) and distinguishes Opus from Vorbis/FLAC in Ogg
Programs that open OPUS files
Windows6 apps
Web Media Extensions (Microsoft)
Free Install from Microsoft Store to add Ogg/Opus playback to Media Player and Edge.
opus-tools (opusdec/opusenc)
Open-source Reference command-line tools: opusdec file.opus out.wav decodes; opusinfo inspects the file. 
macOS2 apps
Linux1 app
VLC media player
Open-source Plays .opus; virtually every Linux player (mpv, Rhythmbox, Audacious) supports it via GStreamer/ffmpeg. 
Android1 app
VLC for Android
Open-source Open the .opus from the Audio tab or a file manager; Android 10+ also plays Opus in many stock players.
iOS1 app
VLC for iOS
Open-source Share/Open the .opus file in VLC - Apple's built-in apps don't support the codec. Technical details
deep spec| Codec architecture | Hybrid of SILK (speech, LPC-based) and CELT (music/general audio, MDCT-based) modes; encoder selects or blends automatically per frame |
| Container format | Ogg container with .opus extension; also embedded in WebM (.weba) and Matroska (.mkv) files |
| Bitrate range | 6 kbps to 510 kbps, configurable and variable per frame |
| Frame size | 2.5 ms to 60 ms; default 20 ms; adjustable per packet for latency vs. quality trade-off |
| Internal sampling rate | Always processed at 48 kHz internally; decoder can output at 8, 12, 16, 24, or 48 kHz |
| Bandwidth modes | Five: narrowband (8 kHz), mediumband (12 kHz), wideband (16 kHz), super-wideband (24 kHz), fullband (48 kHz) |
| Maximum channels | Up to 255 channels in multi-stream Ogg encapsulation (RFC 7845 channel mapping) |
| MIME type | audio/ogg; codecs=opus for file delivery; audio/opus for RTP streaming transport |
| Magic bytes | OggS (hex 4F 67 67 53) at offset 0; OpusHead string at byte offset 28 in the first Ogg page payload |
| Reference implementation | libopus library (BSD-3-Clause licence); opusenc and opusdec CLI tools in the opus-tools package |
| Algorithmic delay | Minimum 26.5 ms look-ahead; low enough for real-time voice and video communication |
| Encoder complexity | Adjustable from 0 (fastest, lowest quality) to 10 (slowest, highest quality) to suit CPU constraints |
| Browser support | Native in Chrome, Firefox, Edge, and Opera; Safari added support from version 11 on macOS and iOS |
| Typical applications | VoIP, WebRTC, podcast and music streaming, voice messages in apps such as Discord and WhatsApp |
| Released | 2012 (codec standardized as RFC 6716, September 2012; Ogg encapsulation RFC 7845, 2016) |
| Open standard | Yes · royalty-free |
| Specification | datatracker.ietf.org |
OPUS conversions
Possible
.OPUS .MP3Online converter
Yes, OPUS converts to MP3 without trouble -- the fastest way on any platform is one ffmpeg command: ffmpeg -i…
How to convert
.OPUS .WAVOnline converter
Yes - ffmpeg or VLC converts OPUS to WAV in seconds with no quality loss.
How to convert
.OPUS .AACOnline converter
Yes, OPUS converts to AAC - the fastest way is a single ffmpeg command.
How to convert
.OPUS .TXTGUIDE
Yes, but not through file conversion: an OPUS file is audio, so getting text out requires a speech-to-text…
How to convert
Not possible
Community Q&A
asked by users
6
Frequently asked questions
How do I play a WhatsApp .opus voice message on my computer?
Open it with VLC media player (free, Windows/macOS/Linux) - it plays .opus out of the box. On Windows you can instead install Microsoft's free Web Media Extensions to use the built-in Media Player.
How do I convert OPUS to MP3?
VLC: Media → Convert/Save → choose MP3 profile. Command line: ffmpeg -i file.opus file.mp3. Online converters work too for non-sensitive recordings.
Why won't my iPhone play .opus files?
Apple's built-in apps (Music, QuickTime) don't support the Opus codec in Ogg files. Install VLC for iOS, or convert the file to MP3/M4A.
Is OPUS better than MP3?
Yes, technically - at the same bitrate Opus sounds clearly better, especially below 128 kbit/s, and it's royalty-free. MP3 only wins on universal device support.
Can I convert OPUS to text (transcribe it)?
Not by file conversion - use a speech-to-text tool: OpenAI Whisper (local/free), Word's transcribe feature, or Google's Recorder. Convert to WAV/MP3 first if the tool rejects .opus.
What app opens .opus on Android?
Android 10+ usually plays them natively (Files by Google, most players); otherwise install VLC for Android. WhatsApp plays its own voice notes internally - the .opus extension appears only on exported files.
Does converting OPUS to MP3 lose quality?
A little - both are lossy codecs, so re-encoding adds generation loss. Use 192 kbit/s or higher MP3 to keep the loss inaudible for voice messages.
References
1RFC 6716 - Definition of the Opus Audio Codecdatatracker.ietf.org
2RFC 7845 - Ogg Encapsulation for the Opus Audio Codecdatatracker.ietf.org
