Disclosure: I run YT320MP3, a free YouTube to MP3 converter. Everything below applies to any converter, including mine, and you can check it yourself with free tools.
Almost every YouTube to MP3 site advertises "320kbps". It sounds like a quality promise. It is really a setting on the output file — and the output can never be better than what YouTube sends.
What YouTube sends
YouTube serves audio separately from video, in a handful of formats. The ones you meet in practice:
| Format ID | Codec | Bitrate | Availability |
|---|---|---|---|
| 251 | Opus (WebM) | up to ~160kbps, variable | almost every video |
| 140 | AAC-LC (MP4) | 128kbps | almost every video |
| 250 / 249 | Opus (WebM) | ~70 / ~50kbps | low-bandwidth fallbacks |
| 141 | AAC-LC (MP4) | 256kbps | YouTube Music Premium only |
(Community reference: https://gist.github.com/AgentOak/34d47c65b1d28829bb17c24c04a0096f — you can list the formats of any video yourself with yt-dlp -F <url>.)
So the best public stream is Opus at up to ~160kbps. There is no 320kbps stream and nothing lossless.
Then why convert to 320kbps at all?
Because MP3 is a less efficient codec than Opus. Re-encoding a ~160kbps Opus stream into a 128kbps MP3 throws away detail a second time. At 320kbps the MP3 has enough room to keep everything the Opus stream contains. So 320kbps is not "better than YouTube" — it is the setting that adds no extra loss.
Where fake 320kbps comes from
Format 140 (AAC, 128kbps) is the easiest stream to grab. Some tools download it and write the result into a file labelled 320kbps. The file is big; the sound is 128kbps AAC that has been converted twice.
How to check any MP3 in one minute
- Install Spek (free, Windows/Mac/Linux).
- Drop the MP3 in.
- Look at the top of the spectrogram:
- content up to ~19–20 kHz → made from a good source such as the Opus stream;
- a hard wall around 16 kHz → made from a 128kbps source, whatever the label says.
Convert the same song with two different sites and compare. The difference is obvious.
What I did with this
When I built YT320MP3 I made the converter always pick the Opus stream first (yt-dlp format selector bestaudio[acodec=opus]/bestaudio/best), decode it once, encode the MP3 once at the bitrate you choose, and add tags and cover art without touching the audio again. No pop-ups, no account, no daily limits.
The longer explanation with the full format table is here: Is YouTube to MP3 320kbps real?
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