Audio conversion without a server
This tool runs FFmpeg — the same engine behind most professional media software — compiled to WebAssembly and executed inside your browser tab. Your file is written into a virtual filesystem in memory, decoded, re-encoded, and read back out. At no point does it travel over the network.
That is a meaningful difference for audio in particular. Voice recordings, interview tapes, and unreleased music are exactly the kind of material people are least comfortable handing to an unknown server, and exactly the kind that most online converters require you to upload.
Lossy and lossless, and why it matters
MP3, AAC (M4A) and Vorbis (OGG) are lossy. They achieve their size by discarding audio a psychoacoustic model predicts you will not notice. The discarded information is gone permanently — decoding an MP3 does not recover it.
WAV and FLAC are lossless. WAV stores raw PCM samples with no compression at all; FLAC compresses those same samples the way a ZIP file compresses text, typically to around half the size, and decodes back to bit-identical audio.
The practical rule: keep your archive lossless and convert to lossy for delivery. Going the other way — converting an MP3 to FLAC — produces a large file containing exactly the same degraded audio, because a lossless format cannot restore what a lossy one removed.
Generation loss
Every lossy re-encode is a fresh round of discarding. Worse, each encoder uses a different model, so the second one does not know what the first threw away and cannot avoid compounding the damage. The audible result is a hollowness in cymbals and sibilance that gets worse with each pass.
If a file has to end up in a specific lossy format, convert to it once, directly from the best source available.
Choosing a bitrate
- 96 kbps — acceptable for speech only; music audibly suffers
- 128 kbps — the long-standing default for podcasts and spoken word
- 192 kbps — transparent for most listeners on most music
- 256 kbps — comfortable headroom for detailed or dynamic material
- 320 kbps — the ceiling for MP3; beyond this the format limits you, not the bitrate
AAC and Vorbis both perform better than MP3 at any given bitrate, so a 128 kbps M4A generally beats a 128 kbps MP3. If the destination supports them, you can drop a step and keep the same perceived quality.