Convert MP3 to M4A
Turn MP3s into M4A files for Apple devices, on your own device.
- Nothing is uploaded
- Works offline after first use
- Open source
- No watermark · limit is your device’s memory; phones hold less
Convert MP3 to M4A (AAC) in your browser for iPhone, Apple Music and ringtones. It is free, needs no account and adds no watermark, and your files are not uploaded: everything runs in your browser on your device. The size limit is your device’s memory, and phones hold less; give the page a short while after your first run to save itself for offline use, and then it works offline.
Done
Open the network tab. Your files never appear in it.
Add files and run the tool to see every request this tab makes.
Your files are processed on this device and never sent to a server. Reload the page to clear everything from memory.
M4A is AAC audio in an MP4 container, the format of Apple Music, iTunes purchases and iPhone voice memos. Some Apple workflows want it rather than MP3: GarageBand ringtones start from an M4A, and some car and podcast apps prefer AAC.
This page decodes each MP3 in your browser and writes an M4A with the browser’s own AAC encoder, which Safari and Chrome or Edge on Windows and Mac include. Nothing is uploaded. Converting from MP3 cannot add quality, so 192 kbps is plenty to keep what the MP3 had.
Before converting, check that you really need an M4A. iPhones, the Music app and iTunes all play MP3 already, so a song library does not have to change. The cases where M4A matters are narrower: a ringtone you are building in GarageBand, an app or car system that only lists AAC files, or a video editor that wants AAC audio. For those, convert just the files you need and keep the MP3s as your originals.
Match the bitrate to the MP3 you start from. A 128 kbps MP3 gains nothing at 256 kbps; it only gets bigger. Pick 192 kbps for most music, or 128 kbps when the MP3 was already 128 kbps or is a podcast. Each conversion throws a little away, so never convert the M4A back to MP3 and then to M4A again. The M4A is written at 48 kHz, the rate AAC encoders in browsers work at.
How it works
- Drop one or more MP3 files, or tap to pick them.
- M4A at 192 kbps is already chosen. Use 128 kbps for speech.
- Convert. Each M4A downloads when it is ready; several come as a zip.
In your browser, not on a server
Your browser decodes the sound with the decoders it uses to play media on any website. The new file is written in your tab: MP3 by LAME compiled to WebAssembly, WAV by a few lines of code, FLAC by a small lossless encoder in this site’s code (fixed predictors and Rice coding, as the FLAC format describes), and M4A or OGG by the browser’s own AAC and Opus encoders (WebCodecs), packed by Mediabunny (MPL-2.0). WAV and FLAC keep the original sample rate.
Compared with upload-based tools: Online audio converters upload every file, queue it, cap free use at a few files or a few hundred megabytes, and keep the upload for hours. Recordings of meetings, unreleased songs and voice memos are private. Here the files never leave your device and a whole folder converts at once.
Verify it yourself. Give the page a short while after your first run to save itself for offline use, then turn off Wi-Fi or switch to airplane mode and run the tool again. Or open your browser's developer tools (F12, or Cmd-Option-I on a Mac), pick the Network tab, and watch it while you convert. The panel above does the same count for you.
Questions
Why does the M4A option not work in Firefox?
Browsers borrow the operating system's AAC encoder to write M4A, and Firefox, like Chrome on Linux, does not have one it can use. Open the page in Safari, or in Chrome or Edge on Windows or Mac. If the file is only going to an iPhone, you can also skip the conversion: iPhones play the MP3 as it is.
Is M4A better than MP3?
A file made from an original recording sounds a little better as AAC than as MP3 at the same size. A file made from an MP3 keeps the MP3’s quality, never more.
Can I make an iPhone ringtone from the M4A?
Yes, with one more step. iPhone ringtones are 30 seconds at most. Cut the part you want first with the MP3 cutter, convert it here, then import the M4A into GarageBand on the iPhone and export it as a ringtone.
Are the song title, artist and cover art kept?
No. The M4A is a new file written from the decoded sound, so the tags from the MP3 are not copied across. If you are adding the files to the Music app, you can type the title and artist and paste cover art in the song's info window after importing.
Is the file uploaded anywhere?
No. There is no server in this process. The page is a static file and the work is done by code running inside your browser tab. Give the page a short while after your first run to save itself for offline use; then you can turn off Wi-Fi and it still works.
More video and audio tools
Audio converter
Turn any sound file into MP3, WAV, FLAC, M4A or OGG. Your files are converted on this device and never uploaded.
Screen recorder
Capture your screen, one window or a tab, with its sound and your voice. The video is made in this tab and never uploaded.
Voice recorder
A voice memo, a voice-over or a quick demo, recorded in this tab and saved as MP3. The sound never leaves your device.
Volume booster
Boost a quiet recording, turn down a loud one, or even out a batch. Done on this device, never uploaded.
Other conversions
Guides
- How to convert WAV to MP3WAV files are large; MP3 is the smaller, more compatible format most people actually need. Here is how to convert between them.
- A free CloudConvert alternative for everyday filesCloudConvert measures its free tier in credits tied to conversion time, not files, which makes it hard to predict when you will hit the limit. Here is an alternative with nothing to meter.
- A free Convertio alternative with no file size capConvertio's free plan caps both file size and how many conversions you get per day. Here is an alternative with no such ceiling.
- How to merge audio filesJoining voice notes, podcast segments or songs end to end is simple once you know the right tool. Here is the desktop way and a private browser way.
- How to reduce MP3 sizeAn MP3 gets smaller when you lower its bitrate, make it mono, shorten it, or switch format. Here is what each saves, with measured results.