Convert WAV to M4A
Shrink WAV recordings into M4A files for Apple devices, on your own device.
- Nothing is uploaded
- Works offline after first use
- Open source
- No watermark · limit is your device’s memory; phones hold less
Convert WAV recordings to M4A (AAC) in your browser, about a tenth of the size, for iPhone and Apple Music. It is free, needs no account and adds no watermark, and your files are not uploaded: everything runs in your browser on your device. The size limit is your device’s memory, and phones hold less; give the page a short while after your first run to save itself for offline use, and then it works offline.
Done
Open the network tab. Your files never appear in it.
Add files and run the tool to see every request this tab makes.
Your files are processed on this device and never sent to a server. Reload the page to clear everything from memory.
A WAV holds uncompressed audio, about 10 MB a minute. AAC in an M4A at 256 kbps, the quality Apple Music sells, is about a fifth of that and sounds the same to nearly everyone, and it plays on every Apple device and in iTunes.
This page encodes each WAV with your browser’s own AAC encoder, which Safari and Chrome or Edge on Windows and Mac include, so the recordings never leave your computer.
Starting from a WAV is the best case for AAC, because the encoder works from the full recording rather than from an MP3 that has already lost detail. That is why 256 kbps is the default here: it is the rate Apple Music sells at, and from a lossless source it is hard to tell apart from the WAV. A three minute song comes out at about 5.8 MB instead of about 30 MB. For voice memos, lectures and interviews, 128 kbps with Mono chosen is plenty, at half the size of 256 kbps.
The M4A is written at 48 kHz and at most in stereo. If your WAV came from a recorder at 96 kHz or 24-bit, the M4A is a listening copy, not a replacement: keep the WAV, or turn it into FLAC on this same page, as the master you edit from. The Music app on Mac and Windows imports M4A directly, but it does not import FLAC, which is the usual reason people need this conversion.
How it works
- Drop one or more WAV files, or tap to pick them.
- M4A at 256 kbps is already chosen. Use 128 kbps for speech.
- Convert. Each M4A downloads when it is ready; several come as a zip.
In your browser, not on a server
Your browser decodes the sound with the decoders it uses to play media on any website. The new file is written in your tab: MP3 by LAME compiled to WebAssembly, WAV by a few lines of code, FLAC by a small lossless encoder in this site’s code (fixed predictors and Rice coding, as the FLAC format describes), and M4A or OGG by the browser’s own AAC and Opus encoders (WebCodecs), packed by Mediabunny (MPL-2.0). WAV and FLAC keep the original sample rate.
Compared with upload-based tools: Online audio converters upload every file, queue it, cap free use at a few files or a few hundred megabytes, and keep the upload for hours. Recordings of meetings, unreleased songs and voice memos are private. Here the files never leave your device and a whole folder converts at once.
Verify it yourself. Give the page a short while after your first run to save itself for offline use, then turn off Wi-Fi or switch to airplane mode and run the tool again. Or open your browser's developer tools (F12, or Cmd-Option-I on a Mac), pick the Network tab, and watch it while you convert. The panel above does the same count for you.
Questions
My browser says it cannot write M4A. What can I do with the WAV instead?
M4A needs an AAC encoder from the operating system, which Firefox and Chrome on Linux do not have. Switch to Safari, or to Chrome or Edge on Windows or Mac. If you only need the WAV smaller and do not need Apple's format, choose FLAC for a lossless copy at about half the size, or MP3 for a small file that plays everywhere.
What bitrate should I choose for a WAV?
256 kbps for music you want to keep and listen to on good headphones. 192 kbps if you need to fit more on a phone and cannot hear a difference. 128 kbps, with Mono chosen, for speech recorded with one microphone. Higher than 256 kbps rarely helps AAC; the 320 kbps option is there if you want to be sure.
How do I get the M4A into Apple Music on my iPhone?
On a Mac, drag the M4A files into the Music app and sync the phone, or turn on Sync Library to have them appear on every device signed in to your Apple Account. On Windows, add them to the Apple Music app or iTunes the same way. Files saved to the Files app play there, but they do not show up in the Music library.
Is the file uploaded anywhere?
No. There is no server in this process. The page is a static file and the work is done by code running inside your browser tab. Give the page a short while after your first run to save itself for offline use; then you can turn off Wi-Fi and it still works.
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