M4A to WAV Converter

Turn an .m4a recording into an uncompressed WAV inside your browser, at its original sample rate. Nothing is sent to a server and nothing waits in a queue.

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M4A to WAV

Konverteren er ffmpeg kompileret til WebAssembly. Det downloades en gang (30 MB), når du vælger din første fil, så forbliver i din browser cache.

Din fil behandles af din egen browser og uploades aldrig. Selve motoren er en engangs 30 MB download første gang du bruger den, og derefter kommer den ud af din browser cache.

Hvordan man bruger M4A to WAV

  1. 1Drop your .m4a files onto the box above, or click it to pick them. Files up to 500 MB are accepted.
  2. 2The converter fetches itself once, about 30 MB of WebAssembly, then decodes the audio.
  3. 3Play the result in place to check it, then download each WAV or take the batch as one .zip.

What the conversion actually does

An .m4a file is an MPEG-4 container with a compressed audio stream inside it, almost always AAC and occasionally Apple Lossless. A WAV file is the opposite idea: a short header followed by the raw samples, written out one after another with no compression at all. Converting M4A to WAV therefore means decoding the compressed stream back into samples and writing those samples down literally.

That is worth being precise about, because it sets expectations correctly in both directions. Nothing is lost in this step, since the decode is exact. Nothing is regained either, because the detail AAC discarded when the recording was encoded is not recorded anywhere. What you end up with is an honest, uncompressed copy of what the M4A holds.

When you want this, and when you do not

Convert when the file is heading into software rather than into your ears. Audio editors, digital audio workstations, game engines, speech to text tools and hardware samplers all handle plain PCM without complaint, while support for M4A ranges from partial to absent. Voice memos recorded on an iPhone are the most common case: they arrive as M4A, and the tool that is meant to transcribe or edit them wants a WAV.

Do not convert m4a to wav when you simply want to play or share the audio. The M4A is already smaller, plays everywhere a WAV does, and sounds identical. Turning a 4 MB file into a 40 MB one for no reason is the mistake this page exists to help you avoid.

Size, speed and the ceiling

Files up to 500 MB are accepted, which is the point at which a browser tab genuinely cannot hold the container in memory. Conversion runs far faster than real time on a laptop, because no picture is involved and no filtering is applied, so the length of the recording is what costs you.

Everything runs locally. The engine is ffmpeg compiled to WebAssembly, fetched once on your first file and cached by your browser afterwards, so the second conversion starts immediately.

Ofte stillede spørgsmål

Will this improve the quality of my recording?
No, and nothing can. M4A almost always holds AAC, which is lossy: detail was discarded when the file was made and it is gone for good. Writing those samples into a WAV stores exactly what survived, in an uncompressed form. You get a file that is faithful to the M4A, which is not the same as a file that is better than it.
Then why convert to WAV at all?
Because a lot of software refuses to open M4A, or opens it badly. Audio editors, DAWs, game engines, transcription tools and older hardware samplers frequently want plain PCM. WAV is the format nothing argues with, which is worth the disk space when a file is about to be edited rather than listened to.
How much bigger will the file be?
Roughly ten times, and often more. A three minute M4A at 128 kbps is about 3 MB; the same audio as a 44.1 kHz stereo WAV is around 31 MB. Uncompressed means every sample is written out in full, so the length and the sample rate set the size, not how complex the music is.
Is the sample rate changed?
No. An 8 kHz mono voice memo comes out as an 8 kHz mono WAV, and a 48 kHz stereo recording stays at 48 kHz. This is why the conversion runs through ffmpeg rather than the browser's own audio engine, which would resample everything to whatever your speakers happen to use.
Where do my files go?
Nowhere. They are read and converted by your own browser. The only thing that travels over the network is the converter itself, once, and your browser caches it afterwards.

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