MP3 (MPEG-1 Audio Layer III) and AAC (Advanced Audio Coding) are built for different jobs. MP3 is typically used for music, podcasts, audiobooks, while AAC is best for apple devices, streaming. Converting lets you open, share or upload your files wherever AAC is expected.
How to use the MP3 to AAC converter
- Add your MP3 filesClick “Choose Files” or drag and drop them into the box. You can add many files at once — or paste a file with Ctrl+V.
- Choose AAC and adjust settingsAAC is selected automatically. Optionally open Settings to change bitrate, sample rate, channels or volume.
- Convert and downloadPress “Convert”. Your AAC files appear instantly — download them one by one or all together as a ZIP.
MP3 vs AAC
MP3 MPEG-1 Audio Layer III
MP3 is the universal audio format. It shrinks music to around a tenth of CD size and plays on literally every phone, car stereo, speaker and app.
- Compression
- Lossy
- Features
- Stereo, ID3 tags
- Origin
- 1993, Fraunhofer IIS
- Best for
- Music, podcasts, audiobooks
AAC Advanced Audio Coding
AAC is the successor to MP3 and sounds better at the same bitrate. It is the default on Apple devices, YouTube and most streaming services.
- Compression
- Lossy
- Features
- Better than MP3 at same bitrate
- Origin
- 1997, MPEG
- Best for
- Apple devices, streaming
Why use ConvertMathly?
Files are processed on your device and never uploaded. Close the tab and they are gone.
No account, no daily cap, no queue and no watermark — convert as much as you want.
The same engine used by professional video tools, running in your browser via WebAssembly.
Windows, Mac, Linux, Chromebook, iPhone and Android — any modern browser, nothing to install.
Frequently asked questions
How do I convert MP3 to AAC?
Add your MP3 files above, make sure AAC is selected and press Convert. The AAC files are ready to download a few seconds later — no installation or account required.
Why does the first conversion take a little longer?
The video engine (FFmpeg compiled to WebAssembly, about 30 MB) is downloaded once and then cached by your browser. After that, conversions start immediately — even offline.
Is there a file size limit?
There is no artificial limit. Because the conversion runs in your browser, the practical limit is your device memory — files up to around 1–2 GB work on most computers. Long videos take longer on phones.
Are my MP3 files uploaded to a server?
No. ConvertMathly converts files entirely inside your web browser using JavaScript and WebAssembly. Your files never leave your computer or phone, which makes it safe for private photos and documents.
Can I convert multiple MP3 files at once?
Yes — add as many files as you like. They are converted one after another and you can download everything in a single ZIP.