Which format should I pick?
MP3 plays everywhere and is the safe choice for sharing. M4A (AAC) sounds a little better at the same size and suits Apple devices. WAV is uncompressed, the usual request from editors and transcription services. FLAC is lossless like WAV at about half the size, good for music libraries. OGG and Opus are open formats that stay small for voice and games.
How audio conversion works here
Audio is decoded and encoded by your browser through WebCodecs, with small open-source encoders for MP3, AAC and FLAC loaded when the browser lacks its own. When the audio already fits the target, as when an M4A becomes AAC, it is copied without re-encoding. Older formats such as WMA and AIFF are opened by FFmpeg compiled to WebAssembly, which downloads once on first use. Read how Myriadfile works for the details.