How to Convert Audio to MP3 on iPhone

Most of Grabio’s audio and video tools run entirely on your iPhone using Apple’s own Shortcuts actions, but MP3 is the one exception. There’s no built-in Shortcuts action that encodes audio to MP3, so Grabio hands the job to VERT, a free, clean converter site, instead of pretending it can do something the iPhone itself can’t.

Why Grabio can’t convert to MP3 on-device

Apple’s Shortcuts app has a native action for converting audio to M4A, which is why converting audio to M4A on iPhone happens instantly and privately, right on your phone. MP3 is different: there’s no equivalent Shortcuts action for encoding MP3, so nothing on iPhone can do this conversion without help from an outside tool.

How to convert audio to MP3 on iPhone with Grabio

1. Add Grabio to your iPhone once, it’s a free Apple Shortcut with no App Store download and no sign-up. Add Grabio to your iPhone.
2. Open the Files app, Voice Memos, or wherever your audio file is, and tap the Share icon on the file.
3. Tap Grabio in the share sheet.
4. Choose Audio → MP3 from the Grabio menu.
5. Grabio opens VERT (vert.sh) in Safari. Because iOS won’t let an app auto-upload a file into a website’s picker, tap the upload area on VERT and select your audio file from the file picker that appears.
6. Choose MP3 as the output format on VERT and download the converted file back to your iPhone.

Is it private and free on iPhone?

Grabio itself is free with no account and no login. Because MP3 encoding has to happen off-device, your audio file is uploaded to VERT’s site for that one step, this is different from Grabio’s fully on-device tools like the M4A converter. VERT is a free tool with no ads clogging the page, but if you want the details of how it stores or handles files, check VERT’s own privacy policy.

Convert audio to MP3 on iPhone: FAQ

Why does Grabio use VERT instead of converting MP3 itself?

Apple’s Shortcuts app simply doesn’t include an action that encodes audio as MP3. Grabio only builds tools it can genuinely deliver, so for MP3 specifically it routes you to VERT rather than faking a conversion it can’t actually do.

Is converting to M4A instead of MP3 a better option?

If the app or device you’re sending the file to accepts M4A, yes, that conversion runs fully on your iPhone with no upload at all. MP3 is still the more universally compatible format for older car stereos, some Android devices, and certain software, so it’s worth it when you specifically need an MP3.

Do I have to select the file manually on VERT?

Yes. iOS doesn’t allow any app, including Grabio, to automatically place a file into a website’s upload box. You’ll need to tap the upload area on VERT and pick your audio file from the picker yourself, this is a one-time extra tap, not a bug in Grabio.

Related on iPhone: convert audio to M4A on iPhone, extract audio from a video on iPhone, or Video & Audio Tools.