Convert between audio formats

MP3, FLAC, WAV and OGG Vorbis — those four and no others. AAC and M4A can go in but cannot come out; if you need an M4A, use a desktop encoder.

MP3, WAV, FLAC, OGG (including .oga and .opus), ADTS AAC and MP4-family files (.m4a, .m4b, .mp4). WMA, AIFF and WebM are refused, so the page blocks them before the upload starts rather than failing at the server.

LAME quality 2, which is variable bitrate averaging about 190 kbps. That is a deliberate default: VBR at this setting is transparent to most listeners and produces a smaller file than 320 kbps CBR for the same perceived quality. There is no bitrate selector on this page.

Yes, unavoidably. MP3 and Vorbis are lossy codecs, so encoding to them discards audio permanently, and doing it twice compounds. Lossless to lossless — WAV to FLAC, or FLAC to WAV — loses nothing at all.

No. FLAC will store the MP3's audio perfectly, but it cannot recover what the MP3 encoder threw away. You get a much larger file containing exactly the same sound.

The encode runs on our CPUs and there is no credit charge, so a sign-in is what keeps the per-account limit of 10 conversions a minute meaningful. Nothing is deducted from your balance.

Most of the wait is the upload, which happens before any encoding starts, and the page shows real upload progress so you can tell the two apart. The encode itself is short — the server allows up to 5 minutes before giving up.

100 MB per file. There is no length limit by default, so a 90-minute recording is fine if it fits under the size cap. Note that converting to WAV inflates the file substantially: uncompressed 16-bit stereo at 44.1 kHz is about 10 MB per minute, so a 20-minute track lands near 200 MB even though the MP3 you started from fitted easily.

Not here — one file per pass. The 10-per-minute limit is per account, so a handful in a row is fine.