Opus
Also known as: Opus audio, .opus file, Opus codec
Opus is a modern, lossy audio format built for high quality at low bitrates. It sounds clearer than MP3 or AAC at the same file size, which is why messaging apps and streaming use it for voice notes and music. It is not lossless, so some original data is discarded.
- Lossy — small files, no exact recovery
- Beats MP3/AAC quality at the same size
- Common in voice notes and web audio
Why Opus files are small
Opus is a lossy format: it shrinks audio by throwing away detail the ear is least likely to notice, then storing what remains far more efficiently than older codecs. At the same file size it generally sounds better than MP3 or AAC, and it scales smoothly from low-bitrate speech up to full music.
That efficiency is why a WhatsApp voice note or a Discord call stays tiny. The trade-off is the same as any lossy format — you cannot recover the exact original audio from an Opus file, only a very close approximation.
Where you run into it
Opus usually arrives inside an Ogg container (`.opus` or `.ogg`) or as the audio track in WebM video. Messaging apps, web audio, and streaming use it heavily.
Most current phones, browsers, and media players handle Opus natively, but some older devices and editing tools do not. If a player rejects it, convert it to a more universal format like MP3 first.