How to Convert MP4 to WAV on iPhone Without an App

Somebody asked you for a WAV. Maybe it is a transcription service that only accepts uncompressed audio, a producer who wants the raw take, a podcast editor with a strict import spec, or a piece of hardware from 2009 that plays nothing else.

Meanwhile what you have is an MP4 video on your iPhone, and iOS gives you no obvious way to turn one into the other.

There are two separate things going on here, and most guides mash them together. The first is pulling the audio out of the video, which your iPhone can do on its own. The second is writing that audio into a WAV container, which it cannot. Splitting them apart makes the whole thing much clearer.

The thing you should know before you convert

WAV is uncompressed. Every sample is stored in full, which is why the format is the standard in recording studios and why the files are enormous. Roughly ten megabytes per minute for stereo CD quality audio. A forty minute recording is about 400 MB as WAV, against maybe 40 MB as M4A.

Here is the part that trips people up. The audio inside an MP4 is almost always AAC, which is a lossy compressed format. Converting that to WAV does not restore anything. It decompresses what is there and writes it out uncompressed.

You get a file ten times larger that sounds exactly the same as the compressed one did, because the detail that compression discarded is gone and no format can bring it back.

That is not an argument against converting. If a tool needs WAV, it needs WAV. It is an argument against believing WAV will improve your audio. It will not. If someone told you to send a WAV because it sounds better, and the source is a video off the internet, they are going to get exactly the same sound in a much bigger file.

Step one: get the audio out, on your device

This half is genuinely native. Apple ships an audio extraction action inside Shortcuts, and it copies the audio track straight out of the video container without re encoding it.

Grabio is a free Apple Shortcut that puts that action in your share sheet.

1. Install Grabio once from Safari on your iPhone.
2. Open Photos or Files and find the MP4.
3. Tap Share, scroll the bottom row, tap Grabio.
4. Choose Extract Audio.

What comes out is an M4A file, saved to Files. No upload, no account, no signal required. You can run it in airplane mode and it still completes, which is the simplest proof that nothing left your phone. The detailed version, including what happens with multi track audio and very long videos, is in extracting audio from a video on iPhone.

Worth pausing here. If the person asking for a WAV would actually accept M4A, you are done, and you did it without uploading anything. Ask before you go further. In my experience about half the requests for a WAV are habit rather than a real requirement, and M4A is accepted by most transcription tools, most editing software and every mainstream player.

Step two: M4A to WAV, which needs outside help

If the requirement is real, the container change is where iOS runs out of road. Shortcuts can convert between the audio formats Apple supports, and WAV output is not something I can promise you from an on device action.

For that, Grabio’s audio conversion hands off to VERT, an open source converter with no ads and no login.

1. In Files, press and hold your extracted M4A.
2. Tap Share, then Grabio.
3. Choose the audio conversion option.
4. Pick WAV as the output and run it.
5. Download the result into Files.

You can also share the MP4 directly and let the converter do both jobs in one pass, which saves a step. I usually extract first anyway, because uploading a 400 MB video to get a 40 MB audio track is a waste of everyone’s bandwidth, and extraction on device is fast.

To be plain about it: this step sends your file to a website. My server never sees it, and what Grabio controls is which site you land on, so you get an open source tool rather than the first search result covered in fake download buttons.

Which Grabio tools are on device and which hand off is set out in how Grabio works. For a confidential recording, do the conversion on a computer instead.

Choosing the settings, if you are offered them

Most converters expose two WAV settings and both matter.

Sample rate. 44.1 kHz is the CD standard and the safe default. 48 kHz is the video and broadcast standard. Match whatever the source was if you know it, and pick 44.1 kHz if you do not. Upsampling to 96 kHz achieves nothing when the source was compressed AAC.

Bit depth. 16 bit is standard and universally supported. 24 bit doubles the file size for headroom you cannot use, since the source has already been through lossy compression. Pick 16 bit unless a studio specifically asked for 24.

If the converter offers mono, and the recording is a single person talking, take it. Mono halves the file size and loses nothing for speech.

What to do about the size

WAV files are the largest common audio format by a wide margin, and this catches people out at the sending stage. Email attachment limits are commonly 20 to 25 MB, which a WAV clears in about two minutes of audio.

Trim before you convert, always. If only four minutes of a forty minute recording matter, cutting the video first turns a 400 MB WAV into a 40 MB one, and no compression trick comes close to that saving. Do the trim in Photos with the yellow handles, it runs on device and takes seconds.

If the whole file has to travel, do not fight the attachment limit. Sending a large file from an iPhone covers the link based routes, and they apply to a large audio file exactly as they do to a video.

When WAV is the wrong answer

Three cases where I would push back on the request.

If it is going into a podcast or onto the web, WAV is pointless as a delivery format, since it will be compressed at the other end anyway. Converting audio to MP3 gets you a universally accepted file that is a tenth of the size.

If it is going onto your own phone to listen to, M4A is better in every way that matters. Same audible quality, far smaller, plays everywhere Apple’s software runs. Converting an audio file to M4A covers it.

If it is going into a video edit, most editing software imports AAC audio directly and converting first just adds a generation of handling for nothing.

WAV earns its size when the audio is going to be processed further, mixed, mastered, or fed into a tool with a hard format requirement. Outside that, it is a large file pretending to be a quality upgrade.

For everything else that will not convert, converting any file format on iPhone is the general guide. And if you want the extraction step sitting in your share sheet, Get the Shortcut, it is free with no login.

Frequently asked questions

Does converting MP4 to WAV improve the audio quality?

No. The audio inside an MP4 is compressed AAC, and converting it to WAV simply decompresses it. Everything the original compression discarded stays discarded. You end up with a file roughly ten times larger that sounds identical. WAV preserves quality that already exists, it does not recreate quality that was lost.

Can I extract audio from a video without uploading it?

Yes. Apple ships an audio extraction action in Shortcuts, so pulling the audio track out of an MP4 happens on your own iPhone with nothing sent anywhere. The output is M4A. It is the container change to WAV specifically that needs an external converter, so if M4A is acceptable you can stay entirely on device.

How big will my WAV file be?

Around ten megabytes per minute for stereo audio at CD quality, so a ten minute recording is roughly 100 MB. Mono halves that. This is why WAV files break email attachment limits so quickly, and why trimming the recording before you convert saves far more space than any setting you can change afterwards.

What sample rate and bit depth should I choose?

44.1 kHz and 16 bit unless someone has specified otherwise. Those are the standard values and everything supports them. 48 kHz is the video and broadcast standard, so match it if your source was video and you know it. Higher settings only add file size, since the compressed source cannot benefit from the extra resolution.

Can iPhone play WAV files?

Yes. iOS plays WAV in the Files app and in most media players without anything installed. The format is not the problem on Apple’s side, the size is. WAV also carries no proper support for artwork and metadata compared with M4A, so it is a poor choice for anything you plan to keep in a music library.

Should I send a WAV or an M4A?

Ask the recipient before assuming. Transcription services, editing suites and most software accept M4A happily, and it is a fraction of the size. Send WAV when there is a genuine technical requirement, typically audio that will be processed or mastered further. Otherwise you are sending a much larger file for no audible difference.