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Glossary · format

What is MP3?

MP3 is the most widely supported audio format. Released in 1993, it's a lossy codec — meaning some audio detail is permanently discarded during encoding. Quality is determined by bitrate (128, 192, 320 kbps). Modern formats (AAC, Opus) sound better at the same bitrate, but no format matches MP3's universal device support.

Also called:mpeg-1 audio layer 3 · audio mp3

MP3 is the answer when you need an audio file that plays on absolutely anything — every car stereo since 2005, every smart speaker, every streaming pipeline, every voice recorder, every phone. Its compression efficiency is dated, but compatibility is its actual feature.

For YouTube audio downloads, MP3 is a transcode (lossy decoding of the source AAC, then re-encoding into MP3 — quality drops twice). The original m4a/AAC is a direct copy with zero quality loss. Pick MP3 only when the destination explicitly cannot play m4a; otherwise m4a sounds better and is smaller at equivalent bitrates.

Common questions

Is 320 kbps MP3 transparent (indistinguishable from source)?
Close, but not quite — golden ears can still spot occasional artifacts. 256 kbps AAC sounds equivalent to 320 kbps MP3 at smaller size. For practical use, 192-320 kbps MP3 is fine.
Why does MP3 from YouTube sound worse than the YouTube playback?
YouTube serves AAC. Converting to MP3 adds a second lossy compression pass on top of the existing AAC encoding. Stay with m4a (AAC) for best quality.

Related terms

M4A

M4A is an audio-only file format that wraps AAC-encoded audio in an MP4 container.

Codec

A codec is the algorithm that encodes (compresses) and decodes raw audio or video into a smaller stream.

Bitrate

Bitrate is the amount of data a video or audio stream carries per second, measured in bits per second (bps) or kilobits (kbps) and megabits (Mbps).

VidPickr is a free, browser-based YouTube downloader. Every term in this glossary either describes how YouTube delivers video or why your downloads behave the way they do. Try the downloader →