MP4 to M4A on iPhone

Safari on iOS 15.4 and newer runs the converter completely, on the phone itself. There is no App Store download — and no converter app quietly uploading your recordings to its own servers. MP4 files convert to M4A here the same way — nothing to install.

If the file is in Voice Memos or Photos, tap the share icon and choose 'Save to Files' first — that makes it visible to Safari's file picker. The converted file lands in Files (Downloads by default), from where you can share it into Messages, Mail, or any app. Your MP4 comes out as M4A, ready to use straight away.

The MP4 files people convert on an iPhone almost always originate from phone video, recorded webinars and lectures, downloaded clips, and screen captures, and the video stream is nearly the entire file, so extracting the audio collapses a 500 MB video into a few MB — which is precisely why they're stuck on the phone until you convert them to M4A.

A minute of MP4 is about 60 MB; the same minute as M4A is roughly 1.2. Across an album or a long recording that difference decides whether it fits on a phone. Re-encoding lossy to lossy compounds artifacts. Convert once, at a high bitrate, and keep the result rather than round-tripping again.

MP4 to M4A is a common iPhone snag specifically because the video stream is nearly the entire file, so extracting the audio collapses a 500 MB video into a few MB, and M4A is what your other apps and devices expect. Apple gives you no built-in way to convert audio at all, so the App Store is full of converter apps — many upload your recording to their own servers, show ads against it, and want a subscription. Doing it in Safari means the MP4 file is processed on the phone itself and stays there, which matters when it is a voice memo, an interview, or a recording of your own family.

Your MP4 file never leaves the handset. For iPhone that is the whole argument: phone video are usually personal, and the App Store alternative frequently ships them to a company's servers as the price of a free conversion. Processing the MP4-to-M4A conversion on-device means there is no server to trust in the first place.

MP4 files come from phone video, recorded webinars and lectures, downloaded clips, and screen captures. The video stream is nearly the entire file, so extracting the audio collapses a 500 MB video into a few MB — which is the whole reason this conversion exists. M4A is the destination because it plays essentially everywhere — iPhone Voice Memos and every ordinary phone, browser, and player. Expect roughly 50× smaller: MP4 runs about 60 MB per minute, M4A about 1.2. Both MP4 and M4A are lossy, so this pair stacks a second encode — at a generous bitrate it stays inaudible, but if a lossless original of the MP4 exists, encode the M4A from that instead.