How to Convert Audio on iPhone: Files App & Browser

iOS does not include a stock audio conversion app. Voice Memos can export the recordings it made, the Files app can move audio around, and Music can play tracks — but none of them convert between formats. To go from M4A to MP3 or WAV to AAC on iPhone alone, you need either Safari plus a browser-based converter, or a third-party app, or a Shortcuts automation. Each path has different limits.

Method 1: Safari Plus a Browser-Based Converter

This is the only zero-install path that handles every common format. AudioUtils runs FFmpeg compiled to WebAssembly inside the Safari tab, so the file never leaves the device — no upload, no account, no app download. It works in Safari, Chrome, Firefox, Brave, and Arc on iOS 14 and later.

Workflow:

1. Open Safari and navigate to audioutils.com (or directly to a tool like /m4a-to-mp3) 2. Tap "Choose File" — iOS opens the Files picker 3. Select the audio file from On My iPhone, iCloud Drive, or Recents 4. Pick output settings (bitrate, sample rate) and tap Convert 5. The converted file downloads to Files > Downloads

Memory ceiling: Safari on iPhone allocates roughly 200–300 MB of WASM memory before the tab gets killed. A 90-minute WAV at 16-bit/44.1 kHz is around 950 MB and will not load. Convert long-form recordings on a Mac or Windows machine, or first downsample to a smaller intermediate format using a third-party app. Most podcast and music files (under 60 MB) convert fine.

Tip: tap the share icon in Safari and "Add to Home Screen" — the converter then launches like a native app icon and benefits from PWA caching.

Method 2: Voice Memos Native Export

Voice Memos records as M4A (AAC) at 44.1 kHz mono by default. The "Lossless" setting (Settings > Voice Memos > Audio Quality) records to ALAC inside an M4A wrapper at 48 kHz mono. Either format exports through the share sheet:

1. Tap the recording in Voice Memos 2. Tap the three-dots menu > Share 3. Pick AirDrop, Messages, Mail, or Save to Files

The exported filename is the recording title with a .m4a extension. There is no built-in MP3, WAV, or AIFF conversion. To get MP3, share the M4A to Files, then open it in M4A to MP3 in Safari.

Method 3: Files App as the Bridge

The Files app is iOS's filesystem UI. It does not convert — but every conversion workflow on iPhone routes through it for storage and handoff. Common patterns:

• Email attachment: long-press > Save to Files > Downloads
• AirDrop received: automatically lands in Files > Downloads (or in the app you chose)
• iCloud Drive sync: edit on Mac, the file appears in Files on iPhone for processing
• Document picker: any browser converter or third-party app pulls from Files for input

Method 4: Third-Party Apps

Several App Store apps handle conversion natively without a browser:

• Documents by Readdle (free) — built-in audio converter for MP3, M4A, WAV, AAC, FLAC. Generous file size limits, also handles ZIP and PDF.
• AnyConvert — broad format coverage, runs locally for most conversions; some formats route through their server.
• The Audio Converter (paid) — single-purpose, supports MP3, M4A, WAV, FLAC, OGG, AAC. ~$3 one-time.
• Audio Format Converter (free with ads) — basic but works offline.

Trade-off: third-party apps are faster than browser-based for large files (multi-GB) because they have full access to iOS storage rather than the Safari WASM sandbox. Browser-based wins on convenience and privacy for files under a few hundred MB.

Method 5: Shortcuts Automation

The Shortcuts app can chain Voice Memos export, file rename, and share-sheet calls into a single tap. Example: a "Record and convert to MP3" shortcut can record, save the M4A to Files, then open Safari to a converter URL with the file pre-loaded via the share sheet target. This does not actually do format conversion inside Shortcuts (Shortcuts has no Convert Audio action as of iOS 17), but it removes friction from the common workflow.

A more useful shortcut: "Send to AudioUtils" as a Files share-sheet action that opens the converter URL directly with the file pre-attached.

Common iPhone Audio Scenarios

• Received a WMA file that won't play. iPhone has no native WMA decoder. Save to Files > open in Safari WMA to MP3.
• Voice Memo too large to email. M4A is already AAC-compressed. Reduce bitrate by re-converting at 64 kbps mono via M4A to MP3 — a 60-minute recording drops from ~30 MB to ~28 MB at the same length.
• Received an AIFF file. Plays natively but eats storage. Convert to M4A for a 10x size reduction.
• MOV from another iPhone. Pull just the audio with MOV to M4A — the AAC track is copied without re-encoding.
• Lossless Voice Memo. ALAC inside M4A. Converts to FLAC losslessly via the converter, or to MP3/AAC for sharing.

Format Limits to Know

iPhone's native players (Music app, Voice Memos, QuickLook in Files) decode MP3, M4A/AAC, ALAC, AIFF, WAV, CAF, and Apple Lossless. They do not decode FLAC outside of recent iOS builds (iOS 11+ added FLAC playback in the Files app QuickLook), OGG Vorbis, Opus, or WMA. If a file format is not on the native list, conversion is the only path to playback.

AirDrop as a Transfer Bridge

When Safari conversion fails on a large file, AirDrop to a Mac and convert there using the workflows in how to convert audio on Mac. The Mac's afconvert utility, FFmpeg, GarageBand, and Music app all handle large files without browser memory ceilings. Once converted, AirDrop the result back to iPhone — it lands in Files > Downloads. Round-trip takes under a minute over a local Wi-Fi network and avoids cloud uploads entirely.

For sensitive recordings (legal, medical, voice notes containing personal information), the AirDrop bridge plus local conversion is the privacy-preserving path; nothing leaves the local network and no cloud service touches the audio.

For broader format context, see how to convert audio on Mac, convert voice memo to MP3 iPhone, and best audio format for Instagram for what to upload after conversion.