Is this MP3 to M4A converter really free?

Yes. Up to 5 files at a time, no signup, no catch. The free tier adds a small watermark to image output — Pro ($9.99/mo or $49/yr) removes it, raises the file size limit to 500 MB, and unlocks unlimited batch conversion.

Are my files uploaded to a server?

No — and you can verify it yourself. Open DevTools → Network tab, then convert a file. You'll see zero upload requests. Everything runs in your browser via WebAssembly. We never see your files.

How long does conversion take?

Usually 1–3 seconds for a typical file. The very first conversion on a fresh page load may take 5–20 seconds while the WebAssembly codec loads — after that it's instant. Your CPU does all the work locally.

What is the file size limit?

Free: up to 10 MB per file, 5 files per batch. Pro: up to 500 MB per file, unlimited batch. If you're working with large videos or RAW photos, Pro is built for that.

Can I batch convert multiple MP3 files at once?

Yes — drop multiple files at once (or Ctrl/Cmd+click to select them) and they all convert in parallel. Free accounts handle up to 5 files per batch; Pro has no limit.

What bitrate will the converted audio use?

We default to 192 kbps for MP3, 128 kbps for OGG/Opus, and 320 kbps for M4A/AAC. These settings are perceptually transparent — most listeners can't tell the difference in a blind test.

Will my metadata (ID3 tags, album art) be preserved?

Yes, when both formats support it. Tags carry over on conversions like MP3→M4A or FLAC→MP3. WAV has limited tag support, so some metadata may not transfer.

How private is this converter?

Completely private — by design, not policy. There is no upload endpoint. Files are processed using WebAssembly inside your browser tab and disappear the moment you close it. We collect only anonymous page-view counts; your file content is never seen or stored.

MP3 to M4A Converter — Free, Fast, In-Browser

How to convert MP3 to M4A online

1
Drop your MP3 file
Drag and drop your MPEG-1 Audio Layer III file onto the converter, or click to browse your files. You can select up to 5 at once. Nothing leaves your device — conversion happens right here in the browser.
2
Hit Convert — it happens locally
Click Convert and watch it go. There's no upload, no server queue, no waiting. The converter runs MPEG-1 Audio Layer III → MPEG-4 Audio entirely in your browser tab using WebAssembly. Most files finish in 1–3 seconds.
3
Download your M4A
Your MPEG-4 Audio file is ready. Click Download, or grab a ZIP if you converted a batch. Close the tab and everything disappears — no copies kept anywhere.

MP3 vs M4A: format overview

MP3

MPEG-1 Audio Layer III

Fraunhofer Society · 1993

Compression: lossy
Transparency: No

✓ Universal compatibility — plays everywhere
✓ Good compression at 128–320 kbps
✗ Lossy — artifacts at low bitrates

M4A

MPEG-4 Audio

Apple / MPEG Group · 2001

Compression: lossy
Transparency: No

✓ Better quality than MP3 at same bitrate (AAC codec)
✓ Native Apple ecosystem support

MP3 magic bytes: 49 44 33 (ID3) / FF FB

M4A magic bytes: 00 00 00 xx 66 74 79 70 4D 34 41

Why convert MP3 to M4A?

If you've ever tried to open a MP3 file and hit a wall — the app won't accept it, the website rejects it, or the preview just shows a broken icon — you already know why this conversion matters.

MPEG-1 Audio Layer III is great for what it was designed for, but it has real-world limitations: lossy — artifacts at low bitrates and lower quality ceiling than flac/aac. The moment you step outside that original context, it gets frustrating fast.

MPEG-4 Audio is the safer choice for iTunes purchased music, Apple voice memos, iOS audio exports. Its main advantages — better quality than mp3 at same bitrate (aac codec) and native apple ecosystem support — mean it just works wherever you need it.

A few common reasons people end up here: - Their target app, site, or device doesn't accept MP3 - They need a smaller file for email or upload (M4A often compresses better) - They need MPEG-4 Audio's specific capability: better quality than mp3 at same bitrate (aac codec) - Compatibility with older software that pre-dates MPEG-1 Audio Layer III

The conversion is one-way: you get a M4A that works everywhere MPEG-4 Audio is expected. The original MP3 file is not touched.

Quality & file size: MP3 to M4A

Typical file sizes: MP3 3–5 MB → M4A 3–6 MB.

Both MP3 and M4A use lossy compression. We transcode at high quality settings (equivalent to M4A's recommended web quality) to minimize generational loss.

Color depth: MP3 supports standard color, M4A supports standard color.

Transparency: MP3 does not support transparency. M4A does not support transparency — transparent areas become solid white.

Frequently asked questions

Privacy: how FormatDrop handles your files

Your MP3files are converted 100% inside your browser using WebAssembly. They are never uploaded to our servers, never stored, and never seen by anyone other than you. This isn't a privacy policy claim — it's an architectural guarantee: our server has no endpoint that receives file bytes.