OPUS vs MP3
Opus beats MP3 clearly, especially for speech and at low bitrates: a voice note at 24 kbps Opus is clearer than 64 kbps MP3. MP3 still wins on compatibility, which is why people convert WhatsApp and Discord recordings to it.
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Choose OPUS when
- Voice notes, podcasts and calls, where it is dramatically smaller.
- Web and app audio in browsers, WhatsApp, Discord and Android.
Choose MP3 when
- Any player, car or editor that does not know Opus.
- Upload forms and transcription services that only accept MP3.
What OPUS actually is
Opus is the best general purpose audio codec available, and it is free. It handles everything from 6 kbps speech to full transparent music, switching approach automatically, with latency low enough for live conversation. Every voice and video call you make almost certainly uses it.
Opus at 64 kbps sounds better than MP3 at 128, so the bitrate you are used to is roughly double what you need here.
What MP3 actually is
MP3 discards the parts of a sound that psychoacoustic models say you are least likely to hear, then compresses the rest. It was the format that made digital music portable, and while newer codecs beat it at every bitrate, nothing matches its compatibility.
Converting an MP3 to another lossy format compounds the damage, because the second encoder is guessing at audio the first one already threw away.
OPUS and MP3 side by side
| OPUS | MP3 | |
|---|---|---|
| Extension | .opus | .mp3 |
| Media type | audio/opus | audio/mpeg |
| Inside the file | Opus | MPEG-1 Layer III |
| Compression | Lossy | Lossy |
| One minute of stereo | 0.25 to 1 MB | 1 to 2.4 MB |
| Plays on | browsers, Android, WhatsApp and Discord, but not many car stereos or older players | everything, including car stereos and hardware twenty years old |
| We can write it | Yes | Yes |
Questions
Why are WhatsApp voice notes .opus files?
Because Opus is the most efficient codec for speech. A minute of voice is around 100 KB.
Does converting Opus to MP3 lose quality?
A little, since both are lossy, but at 64 kbps or more a voice note sounds the same.