MP4 to MP3 on an iPhone

What you need

• An iPhone or iPad running iOS/iPadOS with Safari 26 or newer.
• The MP4 saved as a file, not only in Photos.
• Enough free space for the MP3. The MP3 is much smaller than the video.

Safari 26 is the first version with WebCodecs audio decoding. On an older iOS, the page checks the capability and tells you it cannot run. It does not pretend to convert and fail at 99%.

Step by step

1. Save the video to Files. In Photos, open the clip, tap Share, then Save to Files. Pick iCloud Drive or On My iPhone.
2. Open the converter in Safari. The home page is the tool.
3. Choose the file. Tap the drop area, then browse to the file you just saved.
4. Pick a bitrate. 128 kbps is enough for speech; 192 kbps is a good default; 320 kbps is the maximum.
5. Convert. Keep Safari in the foreground. The progress bar shows decoding and encoding.
6. Save the MP3. Tap Download. If the file opens in a player instead of saving, long-press the download control and choose Save to Files.

Why the Files step matters

The browser can only read a file the system gives it. A video that lives only in Photos is not automatically available to Safari’s file picker. Saving it to Files gives you a stable file the browser can read, and it makes the conversion independent of the Photos library.

If the clip is in iCloud Drive and not downloaded yet, wait for the download to finish before starting. A partial file looks like a truncated MP4 to the converter.

iPhone-specific limits

Memory. A long 4K clip can be several gigabytes. The converter reads it lazily, but decoding and encoding still need memory. If Safari reloads the tab, the device ran out; trim the clip or use a Mac.

Background suspension. Switching apps or locking the screen can pause the tab. Keep it open until the result appears.

Thermal throttling. A long conversion on a warm phone slows down. This is normal; the output is still being written locally.

No app install. There is no profile, no shortcut and no App Store dependency. The trade-off is that the tool is a web page, so it cannot run in the background like a native app.

When a Mac is the better device

• The video is longer than a few minutes.
• The file is above 1 GB.
• You need a batch of files.
• You want to check the source bitrate with ffprobe first.

The Mac route is documented separately: MP4 to MP3 on a Mac. Both routes keep the file local; the difference is memory, screen size and how easy it is to keep the process in the foreground.

FAQ

Can I convert an MP4 to MP3 directly from Photos?

Save it to Files first. Photos does not expose the video to the browser's file picker in the same way, and a large video is easier to handle as a Files item. In Photos, tap Share → Save to Files, then open the converter in Safari and choose that file.

Where does the MP3 go on iPhone?

It goes to the Downloads folder in Files, or to the location you choose in the share sheet. Long-press the download button and choose Save to Files if the default location is not what you want.

Why does the conversion stop when I switch apps?

iOS can suspend a background tab. Keep Safari in the foreground until the progress bar finishes. The conversion itself runs on the device; it is not waiting for a server.

Does it work on older iPhones?

Only if the device runs Safari 26 or newer. The limit is the browser's WebCodecs audio decoder, not the CPU. On an older iOS version, use a Mac or PC for the conversion.

Is there an app that does this?

There are App Store converters, but they are not required for a format change this small. The browser route avoids an install, an account and a second copy of the file. The trade-off is that the tab must stay open while it works.

Are my videos uploaded?

No. The file is read through the browser's File API and processed in the tab. There is no upload endpoint.

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