twineconvert
Free · in-browser · no upload

MP3 to M4A
Converter

Drop your MP3 file. We'll convert it to M4A right here in your browser, your file never leaves your device.

Local

Drop your file here

or click to pick from your device

.mp3
Nothing uploaded No file size cap Open source

How it works

Three steps. No upload, no signup.

  1. 1

    Drop your file

    Click the dropzone above or drag a MP3 from your desktop. Files of any size, there's no upload, so there's no upload limit.

  2. 2

    Convert in your browser

    The conversion runs entirely in this tab using JavaScript and WebAssembly. Your file never touches our servers, we don't have any.

  3. 3

    Download

    Get your M4A the moment the conversion finishes. Convert another, or close the tab.

Files stay on your device

Your file is never uploaded. The entire conversion runs in your browser using WebAssembly. We can't see what you convert because we have no server to see it.

No file size limit

Server converters cap free users at 1-2 GB and gate larger files behind a paid plan. Since nothing uploads, our limit is whatever your browser can handle.

Free, no signup, no ads on conversions

No account required. No watermark on the output. No queue. Open source, every line of conversion code is public.

Formats involved

About MP3 and M4A

MP3, MPEG Audio Layer III

MP3 is the most widely-supported audio format ever, every device, app, and music player on the planet reads it. It uses lossy compression (typically removing audio frequencies humans can't hear well) to shrink files to about a tenth of their uncompressed size. At 192 kbps and above, the difference vs lossless is inaudible to most listeners on most equipment.

How to open

Every audio player ever made. iOS Music, Android, VLC, iTunes, Windows Media Player, browsers, smart speakers, universal.

Full MP3 format guide →
M4A, MPEG-4 Audio

M4A is AAC-encoded audio inside an MP4 container, Apple's preferred audio format. Higher quality than MP3 at the same bitrate (AAC is a generation newer than MP3). All Apple devices use it natively; iTunes/Apple Music ripped CDs as M4A by default. Compatibility on non-Apple devices has improved dramatically, most modern Android and Windows players read M4A directly.

How to open

All Apple devices, modern Android/Windows players, VLC, browsers (HTML5 audio). Older feature phones and some car stereos may need MP3 instead.

Full M4A format guide →

Convert your MP3 to other formats

How we compare

MP3 → M4A vs the alternatives

FeatureUstwineconvertCloudConvertiLovePDFFreeConvertSmallpdf
Files uploaded to a server
Free file size limitNo limit1 GB200 MB1 GB5 GB
Free conversions per dayUnlimited10/dayLimitedLimited2/day
Signup required
Watermark on output
Open source
Works offline (after first load)

Last verified May 2026 from each competitor's pricing and FAQ pages. Limits and pricing change frequently.

FAQ

Common questions

Is this MP3 → M4A converter really free?

Yes. No signup, no watermark, no daily file count limit. The entire engine is open source, you can read the conversion code on GitHub.

Where does my file go when I convert it?

Nowhere. The conversion runs entirely in your browser using JavaScript and WebAssembly. Your file is never uploaded to our servers. We don't have any servers handling files, there's nothing for us to log, store, or accidentally leak.

What's the maximum file size?

Whatever your browser can hold in memory. Practically, this means a few hundred MB on most computers, significantly larger than the 1-2 GB caps that server-upload converters charge for. Very large files (multi-GB) may require closing other browser tabs first.

Why convert MP3 to M4A?

Music files, podcasts, audiobooks, voice recordings. Higher-quality audio than MP3, especially in Apple ecosystems. The most common reason to convert is compatibility, M4A works in places where MP3 doesn't, or vice versa.

How do I open a MP3 file in the first place?

Every audio player ever made. iOS Music, Android, VLC, iTunes, Windows Media Player, browsers, smart speakers, universal.

Does this work offline?

Once the page is loaded, the conversion itself runs entirely offline. The first time you use a tool, your browser downloads the conversion library (a one-time cache). If you reload while offline, the page won't load, but you can install the site as a Progressive Web App for full offline use.

Can I convert multiple files at once?

Single file at a time for now. Batch conversion is on the roadmap, for now, drop one file, download the result, then convert the next.