Audio converter — MP3, WAV, M4A, OGG, FLAC

How to use it

1. Choose an audio file — MP3, M4A, WAV, FLAC, OGG and more all work.
2. Pick the format you want out: MP3 for universal support, WAV or FLAC for lossless, M4A or OGG for efficient compression.
3. Press Convert — the first run downloads the audio engine once, then the converted file downloads.

Each lossy encode is a permanent decision, and they stack

A lossy encoder does not compress evenly. It runs a psychoacoustic model over the signal, predicts which detail will be masked by louder sound nearby, and deletes that detail outright. The deletion is final and no later step can reason it back, which is why converting an MP3 to FLAC yields a bit-perfect, considerably larger copy of an already-thinned signal rather than a repaired one.

Chaining different lossy formats is worse than repeating one, because the models disagree. Detail MP3 kept because it judged it audible may be exactly what Opus or AAC discards on its own reasoning, and the reverse, so each pass removes a different slice and the slices accumulate. The habit that avoids this is to keep the least-compressed copy you have and convert from that every time, rather than converting yesterday’s conversion.

Opus is the better codec, MP3 is the one that plays anywhere

The quality-per-kilobyte gap is real and widest at the bottom of the range. Opus at 64 kbps is broadly comparable to MP3 at around twice that, and it stays usable far lower still, down to about 32 kbps for speech, where MP3 has long since dissolved into warbling. It also handles speech and music in one codec and encodes with very low latency, which is why it carries most real-time voice traffic on the internet.

None of which helps if the thing playing the file cannot decode it. MP3 is understood by car head units, gym equipment, DJ controllers, in-flight entertainment and a generation of hardware that stopped getting firmware updates a decade ago. Choose by destination rather than benchmark: MP3 when the file leaves your control, Opus or AAC when you know what will open it, FLAC when it is an archive you expect to re-encode from later.

Questions