AudioConvert
Convert audio to WAV
Turn an M4A, FLAC, OGG, AIFF or MP3 recording into a WAV, and trim, fade or level it on the way through. The decoders are the ones your browser already carries, so the work happens in the tab you are looking at.
Output is WAV. There is no MP3 encoder on this page — shipping one means shipping a licensed encoder, and a re-encode would lose quality that the original still has.
Convert M4A, FLAC, OGG, AIFF or MP3 to WAV, with trimming, fades and levelling. Which files open here depends on the decoders your own browser ships with, so a format one browser reads may be refused by another — the page says which it managed.