Convert MP4 to M4A Online
Extract M4A audio from any MP4 video. Stream copy with no quality loss. Free, in your browser.
.mp4 · up to 100 MB
What you can do
MP4 to M4A: the most direct pipeline for Apple audio
Stream copy = zero loss
If the MP4 already has AAC audio, extraction is bit-for-bit identical to the original. No recompression.
iPhone ringtone in minutes
Extract the M4A, rename it to .m4r and you have your custom ringtone ready to import to iOS.
100% private
Your video never leaves your device. FFmpeg.wasm processes everything locally in WebAssembly.
Apple Music library
M4A is the native format for iTunes and Apple Music. Import with full metadata and cover art.
How it works
Three steps, no hassle
Upload your MP4 file
Drag or select your .mp4 video — iPhone recording, YouTube clip, camera video, or screencast. Up to 500 MB, no signup.
M4A audio extraction
FFmpeg.wasm analyzes the MP4 container. If audio is already AAC (virtually all modern devices), it performs a direct stream copy to the M4A container — maximum speed and zero additional loss.
Download your M4A file
Get audio ready for iTunes, Apple Music, podcast libraries, or rename it to .m4r to turn it into a custom iPhone ringtone.
FAQ
Got questions?
Both are based on the ISO Base Media File Format (ISOBMFF, ISO/IEC 14496-12). The difference is functional: .mp4 indicates the file can contain video, audio, and subtitle tracks; .m4a (MPEG-4 Audio) explicitly signals audio-only content without video. Apple introduced the .m4a extension to differentiate pure audio files in iTunes. Technically, an M4A is an MP4 with the video track removed — the moov, trak, and mdat atoms are structurally identical. This similarity is precisely what enables stream copy — FFmpeg simply moves AAC samples from the MP4 container to the M4A container without touching the encoding.
Yes, in the strict technical sense. When audio inside the MP4 is already encoded as AAC — which is the case for virtually all videos recorded with iPhone, iPad, GoPro, Sony ZV-E10, Canon EOS R, Samsung Galaxy, and YouTube videos above 360p — FFmpeg performs a stream copy: it doesn't decode or re-encode the audio, it simply moves AAC packets from one container to another. The result is bit-for-bit identical to the original audio. No additional compression generation is introduced.
The full process: extract the M4A here, download the file, rename the extension from .m4a to .m4r on your computer. Then connect the iPhone to your Mac, open Finder (macOS Catalina and later) or iTunes (Windows), drag the .m4r to the Tones section of the device and sync. Alternatively, on iOS 15 and later you can import directly from Files using GarageBand as an intermediary. The ringtone must be 40 seconds or less to be accepted by iOS.
Completely. M4A is Apple's native audio format: iTunes (Windows and pre-Catalina macOS), macOS Music app, Apple Music on iOS/iPadOS, and AirPods Pro and Max with Spatial Audio. When importing an M4A to the library, iTunes reads metadata from the udta atom, including title, artist, album, cover art (in the covr atom), and date. For uploading to Apple Music via independent distributors (DistroKid, TuneCore, CD Baby), M4A in AAC-LC at 256 kbps is accepted as an alternative delivery format to WAV.
FFmpeg automatically selects the first audio track (stream 0:a:0) for extraction. In MP4 videos with multiple languages or director commentary, this means you get the first available language/track. If you need a specific track, the FFmpeg command-line tool lets you select it with: ffmpeg -i video.mp4 -map 0:a:1 -c:a copy track2.m4a — where 0:a:1 selects the second audio track (zero-based index). This advanced track selection is not available in the current web version.
Yes. Apple Podcasts accepts M4A/AAC audio in RSS feeds. Apple's technical requirements for podcasts specify AAC-LC (not HE-AAC) at 128 kbps mono or 192 kbps stereo, with 44.1 kHz or 48 kHz sample rate. If your original video was recorded with those audio specs, the extracted M4A directly meets the requirements without additional transcoding. Platforms like Buzzsprout, Podbean, Transistor, and Anchor (Spotify for Podcasters) also accept M4A natively.
Convert MP4 to M4A: extract audio for Apple Music, iTunes, and iPhone ringtones
Converting MP4 to M4A is one of the most technically efficient audio extraction operations possible, and the reason lies in the shared architecture of both formats. The MP4 container (MPEG-4 Part 14, ISO/IEC 14496-14) and the M4A container are both variants of the ISO Base Media File Format (ISOBMFF, ISO/IEC 14496-12): they share exactly the same box atom structure — ftyp, moov, mdat, free — and the same metadata scheme in the udta atom. The only difference is that M4A omits video tracks and uses the FourCC 'M4A ' in the ftyp box's compatible brands field to signal that the content is audio-only. This structural identity makes stream copy possible: when the MP4 contains AAC audio (virtually all modern recording devices use AAC-LC by default — iPhone since the iPhone 3GS with iOS 3, GoPro Hero since 2010, Sony Alpha and Canon EOS cameras since 2012), FFmpeg can transfer AAC packets from the MP4 container to the M4A container by literally moving data between containers without touching a single audio sample. The result is a conversion that can process a 1 GB file in seconds, preserving audio with bit-for-bit identical quality.
The use cases that make MP4 to M4A a high practical-value conversion in 2025 cover three main workflows in the Apple ecosystem. The first and most common is the iPhone ringtone pipeline: the .m4r files that iOS accepts as custom ringtones are technically M4A files with the extension renamed — there is no internal technical difference between a .m4a and a valid .m4r. The full process is extracting the M4A here, trimming to under 40 seconds (with GarageBand for iOS, iMovie, or FFmpeg), renaming to .m4r, and importing through Finder on macOS or iTunes on Windows. The second workflow is iTunes and Apple Music library organization: when you record videos with an iPhone and want to archive only the audio, M4A is the native format iTunes recognizes as audio without requiring any additional plugin, and it supports all the metadata Apple Music indexes — title, album, artist, genre, cover art, and lyrics. The third workflow is podcast distribution: content creators who record on video and need to distribute on podcast platforms get an M4A directly ready to upload to Apple Podcasts Connect, Buzzsprout, Transistor, or Podbean without additional intermediate steps.
Convertir.ai runs MP4 to M4A conversion entirely in the browser using FFmpeg.wasm. The technical process begins with parsing the ftyp box to confirm ISOBMFF compatibility, followed by analysis of the moov box to locate the trak atoms describing each media track. The hdlr atom within each trak identifies the handler type: 'vide' for video, 'soun' for audio. FFmpeg locates the first track with hdlr='soun' and examines the stsd atom to determine the codec: if the FourCC is 'mp4a' (AAC in all its variants: LC, HE-v1, HE-v2), full stream copy proceeds. If the FourCC is different (such as 'mp3 ' for MPEG Layer 3 or 'ac-3' for Dolby Digital, present in some Windows-origin MP4 files), FFmpeg transcodes to AAC-LC at 192 kbps by default. The moov box of the resulting M4A contains an ftyp atom with major brand 'M4A ' and compatible brands including 'M4A ', 'mp42', and 'isom', exactly as audio files generated by iTunes, guaranteeing maximum compatibility across the Apple ecosystem. Since all processing occurs in WebAssembly inside the browser with no communication with external servers, the content of the original video — whether personal recordings, musical rehearsals, or confidential material — remains completely private at all times.