320kbps MP3 is widely marketed as the highest quality MP3 format. Before choosing it for YouTube downloads, you need to understand what YouTube's audio infrastructure actually provides — because the answer changes which format is the smarter choice for audio quality.
YouTube stores audio at a maximum of 256kbps AAC for most content, with 128kbps and 48kbps versions for mobile streaming. When you download YouTube audio as a 320kbps MP3, the process is: YouTube's 256kbps AAC source is decoded then re-encoded to 320kbps MP3. This transcoding step applies a second lossy compression process on top of the existing 256kbps AAC compression. The result is a 320kbps MP3 that was derived from 256kbps AAC — it contains all the audio degradation from the original AAC compression plus any additional artifacts from the MP3 transcoding. The 320kbps specification describes the bitrate of the output MP3 file, not the quality of the audio it contains.
FLAC (Free Lossless Audio Codec) downloads from YouTube contain the 256kbps AAC audio decoded to a lossless container — no re-encoding, no additional compression, no transcoding artifacts. You get the highest fidelity representation of what YouTube's servers actually have for that audio without any additional quality degradation on top. If you care about audio quality, FLAC is the better choice for YouTube downloads because it avoids the unnecessary transcoding step that 320kbps MP3 adds. The FLAC file will be larger but audibly equal to or better than the 320kbps MP3 derived from the same source.
320kbps MP3 remains the right choice when file size and compatibility matter more than marginal quality differences. MP3 is compatible with every device and music player without exception — older car stereos, budget earbuds, ancient iPods, every streaming and music management app. FLAC requires a player that supports it, which includes all modern apps but excludes older hardware. If you are building a music library for maximum device compatibility, MP3 at 320kbps is a practical standard even though FLAC is technically the better quality choice for YouTube content.
To specify exactly 320kbps MP3 via command line: yt-dlp -x --audio-format mp3 --audio-quality 0 "YOUTUBE_URL". The --audio-quality 0 flag sets the highest quality VBR MP3 encoding, which averages around 245kbps — equivalent to a constant 320kbps encoding in perceived quality at a slightly smaller file size. For exactly 320kbps CBR: --audio-quality 320K.
yt-dlp can embed metadata — song title, artist, album art from the video thumbnail — into downloaded MP3 files. Add --add-metadata --embed-thumbnail to your yt-dlp command to include this information. The resulting MP3 displays correctly in music library apps with proper title, artist, and thumbnail rather than a generic filename. For large music collections, this metadata embedding saves significant time organizing your library manually.