Sharing and editing want different files
MP3 plays everywhere and throws away some of the sound to stay small. WAV and FLAC keep what was recorded and take more space. Turning an MP3 into WAV does not repair it. That single fact prevents a lot of wasted time.
Voice memos from an iPhone are often M4A. Podcast hosts usually want MP3. Music you might edit later should stay WAV or FLAC until the edit is finished.
If you already know the job, start with MP3 to WAV or WAV to MP3.
Every format on the site is listed from the homepage.
Lossy audio does not heal
Open the tool that names your two formats and read what the download will contain before you delete the original. If a result does not match that description, tell us.
Pick the archive and the copy you send
Keep WAV or a real FLAC while you edit. Send MP3 when the other person, the car, or the podcast host needs a file that plays everywhere. AAC and M4A suit Apple workflows. OGG and Opus suit browsers and some games, and they fail in a lot of cars. AIFF is the uncompressed Mac cousin of WAV.
The conversion that wastes the most time is MP3 to WAV or MP3 to FLAC in the hope of better sound. The new file is larger and it contains the same lossy take. Say so if you share it. Encode to MP3 once, at the end, from the best master you have. Speech can use a lower setting than music.
Cut, join, and speed tools re-encode. They are not a studio waveform editor. The joiner will not even out volume. The speed change can make a voice thin. The first run downloads the converter onto your device. Convert only recordings you have the right to use.
Label the master and the copy differently so you do not edit the MP3 by mistake. If a client asks for WAV, ask whether they mean an uncompressed recording or merely a file their software will import. Those are different requests. The second one can be an MP3 wrapped as WAV, and you should not pretend it is the first. Convert only audio you have rights to use. A three minute true WAV is tens of megabytes. If the file you received is only a few megabytes, it is not that WAV, whatever the name says.
Name the master so you do not edit the copy
The master is the WAV, AIFF, or real FLAC you recorded or received from the studio. The copy is the MP3, AAC, M4A, OGG, or Opus you send. Put the word master in the master name. Put the destination in the copy name. A file that is only a few megabytes for a three minute song is not a WAV, even if someone renamed it. Trust the size and the playback, not the extension someone typed.
Finish edits on the master. Encode once. Do not turn the MP3 back into WAV and call it restored. Speech can be smaller than music. Convert only recordings you have the right to use. The first run downloads the converter onto your device.
Leave headroom in the file name for the version. Master-1, edit-2, and delivery-mp3 are enough. Do not stack words like final-final. When a client says the MP3 is quiet, fix the master and export again. Raising volume on the MP3 and saving it again adds another lossy pass and a new file that is harder to match to the session. Quiet is a mix problem. The format change did not cause it.