What WAV and M4A actually contain
A WAV file is uncompressed PCM audio in Microsoft's RIFF container. Every sample is stored as is, which is why a stereo CD-quality WAV takes about 10.1 MB per minute. It is the working format of recording and editing.
M4A is the audio-only form of the MPEG-4 container (MPEG-4 Part 14), popularised by Apple through iTunes. Most M4A files hold AAC (Advanced Audio Coding), a lossy codec standardised by MPEG in 1997 as the successor to MP3. An M4A can also hold ALAC, Apple Lossless, but AudioDrop's M4A output is always AAC.
AAC removes sounds that listeners are unlikely to hear, based on a model of human hearing. At the same bitrate it generally sounds cleaner than MP3, particularly on cymbals and reverb tails.
WAV to M4A: size and quality side by side
| WAV (16-bit/44.1 kHz) | M4A (AAC) | |
|---|---|---|
| Compression | None | Lossy, perceptual |
| Quality | Lossless, exact | Very good; not identical to source |
| Size per minute | ≈ 10.1 MB | ≈ 1.44 MB at 192 kbps |
| Five-minute song | ≈ 50 MB | ≈ 7 MB |
| Compatibility | Everywhere, but large | iPhone, Mac, Android, most players |
| Best for | Editing, mastering, archiving | Listening, sharing, phone libraries |
When it makes sense to convert WAV to M4A
The usual reason is space. A voice memo exported as WAV, a bounce from your DAW or a ripped album can fill a phone quickly. Turning it into M4A keeps it listenable at a fraction of the size.
M4A is also the native choice in the Apple world. It plays in Apple Music, QuickTime, Safari and Files without any extra app, and it is accepted by many podcast hosts and messaging apps that reject large WAV files.
Quality: what you keep and what you lose
Going from WAV to M4A is a lossless-to-lossy step. Some detail is discarded to make the file small, and it cannot be recovered later by converting back to WAV. At 192 kbps, which is AudioDrop's default for AAC, most people cannot tell the difference from the WAV on normal headphones or speakers.
Treat the M4A as a listening copy. Keep the WAV if you might edit, remix or master the track again, because re-encoding an already lossy file adds a second round of loss each time.
Browser support and settings
M4A output uses the AAC encoder built into your browser rather than one AudioDrop ships itself. That has a few practical effects.
- Chrome, Edge and Safari support AAC encoding, on desktop and mobile.
- Firefox may not support AAC encoding. If M4A fails there, switch browser or pick MP3 instead.
- The sample rate follows your WAV where the encoder supports it.
- Tags such as artist and title in the WAV may not be carried into the M4A.
Picking between M4A, MP3 and keeping the WAV
If every listener is on an Apple device, M4A is a natural choice. AAC is efficient, so 192 kbps sounds clean and a ten-minute recording lands at around 14 MB instead of 100 MB.
If you are sending audio to people on unknown devices, or to older car stereos and MP3 players, MP3 is the safer option because it plays almost everywhere. If you are handing off stems, masters or anything that will be edited, send the WAV or convert it to FLAC so nothing is thrown away.
Voice memos and lectures are a good fit for WAV to M4A. Speech is easy to compress, and the files become small enough to email or upload to a course platform.
How AudioDrop keeps your files private
This WAV to M4A converter runs in your browser using WebCodecs and WebAssembly. Your recordings are never uploaded to a server, there is no account, and nothing is watermarked.
After the page loads you can go offline and keep converting. Batch jobs run several files in parallel and each M4A downloads individually. There is no fixed size limit, although very large files are bounded by your device's memory.