MP3 to M4A

To convert MP3 to M4A, set the Bitrate dropdown first (96k, 128k, 192k recommended, 256k, or 320k), then drag and drop your MP3 files onto the drop area, or click it to choose them, and conversion to M4A starts automatically with each finished file appearing as a row with a Download button. You can add several MP3 files at once; they convert one after another, and every row shows the new filename, its size, and an inline player so you can listen before downloading. The whole job runs in your browser through a WebAssembly build of FFmpeg, so nothing is uploaded to a server.

A little, yes - both MP3 and M4A are lossy formats, so converting one to the other re-encodes already-compressed audio and shaves off a small amount more, and it cannot restore or improve anything the original MP3 already discarded, though the change is usually hard to hear. Choosing 256 or 320 kbps minimises the extra loss, at the cost of a larger file. If you want zero further loss, keep your original MP3 as the master copy.

M4A is AAC audio in an MP4 container and the native format of iTunes, Apple Music and the iPhone, so converting MP3 to M4A makes your files fit cleanly into an Apple library where tags, artwork and chapters behave as the Music app expects. AAC is also MP3's more efficient successor. That said, MP3 remains the most universally compatible audio format, so if you need an old car stereo, a cheap player or an unusual device to play the file, staying on MP3 is the safer bet.

Match or stay near your source MP3's bitrate - there is little point encoding a 128 kbps MP3 to 320 kbps M4A, since the extra bits cannot recover detail that was never there, so 192 kbps (the default) is a sensible choice for most music. Choose 256 or 320 kbps only when the source MP3 is genuinely high quality, and drop to 96 or 128 kbps for podcasts, audiobooks or voice memos. Set the bitrate before adding files, since it is read as each one converts.

It is completely free and fully private, with no signup, no account, no watermark and nothing to install, and your audio never leaves your computer, because the conversion runs inside your own browser through a WebAssembly build of FFmpeg, so no file is ever uploaded to a server. That makes it safe for unreleased music, client recordings, confidential interviews and anything else you would not want sitting on someone else's machine.

There is no limit set by this site, because nothing is uploaded - the only real ceiling is your own device's memory, and since MP3 files are already compact, most convert quickly even in a batch, though a multi-hour recording can still tax a phone. For hundreds of megabytes at once, a desktop or laptop browser is the safer choice, since it has far more memory than a phone. The converter itself is a one-time ~32 MB download on first use, then cached so later conversions start instantly.

Yes - it runs in any modern browser on Windows, Mac, Linux, iPhone and Android, with no app to install, and because M4A is Apple's standard audio format, converted files drop straight into the Music app, iTunes or a Mac library without any extra step. For very large batches a desktop or laptop browser is the safer choice, since phones have far less memory to work with. Everything happens locally, so once the tool has loaded you can even convert with the connection off.