.mp3 — MPEG Audio Layer III
Audio audio/mpeg
What a .mp3 file is
The lossy audio format that made digital music portable. Patents expired in 2017, so it is now completely unencumbered.
How to open it
Everything.
Worth knowing
Modern codecs (AAC, Opus) sound better at the same bitrate, but nothing matches MP3 for universal compatibility.
How to identify a .mp3 file
A file's extension is only its name — renaming a.png to a.mp3 changes nothing inside. What software actually reads is the magic number, the first few bytes of the file.
| Signature | 49 44 33 or FF FB |
| MIME type | audio/mpeg |
| Category | Audio |
"ID3" when there is a metadata tag, otherwise a raw frame header.
# what is this file really?
file mystery.mp3
# look at the first bytes yourself
xxd mystery.mp3 | head -2
head -c 16 mystery.mp3 | xxd
# Windows PowerShell
Get-Content mystery.mp3 -AsByteStream -TotalCount 16 | Format-HexFrequently asked questions
What is a .mp3 file?
The lossy audio format that made digital music portable. Patents expired in 2017, so it is now completely unencumbered.
How do I open a .mp3 file?
Everything.
Is .mp3 safe to open?
Yes. A .mp3 file is data, not code — opening one cannot execute anything by itself.
Can I change a file's extension to convert it?
No. Renaming changes the label, not the bytes. The one place it appears to work is between formats that genuinely share a container — renaming .docx to .zip works because a DOCX is a ZIP. Everything else needs a real converter.