Convert MP4 to AAC
Pull the sound out of your MP4 and keep it as an AAC, leaving the picture behind. MP4 is the video file that plays everywhere: phones, TVs, browsers, editors and every social platform. Your file never leaves your computer.
How to convert MP4 to AAC
- 1 Drop your MP4 .mp4 file onto the page, or click to browse for it.
- 2 Choose the sound quality, or lift the existing track out untouched where that is possible.
- 3 Convert. The work happens on your own machine, so how long it takes depends on your computer and the file.
- 4 Download the AAC, or add more files and do the whole set in one go.
Why convert MP4 to AAC
- You only want the sound: a lecture, an interview, a podcast that was filmed, or a track to listen to with the screen off.
- Better quality than MP3 at any comparable file size.
- Plays everywhere without draining the battery.
- Streaming services and broadcast delivery.
- MP4: fussy about subtitle tracks and unusual audio tracks.
MP4 compared with AAC
How the two formats differ on the things that decide whether a conversion is worth making.
| Property | MP4 | AAC |
|---|---|---|
| File extension | .mp4 | .aac |
| Introduced | 2001 | 1997 |
Quality and what changes
Whether anything is lost depends on the codec. If the track already matches the target, it can be copied out untouched and the audio is bit for bit what was in the MP4. Choosing a different codec means decoding and re-encoding, which is a second generation of lossy compression on top of whatever the video already applied. Encoding at 192 kbps or above keeps that second generation inaudible for most material.
- One AAC limitation to keep in mind: opus sounds better in very small files.
Questions about MP4 to AAC
Will converting MP4 to AAC lose quality?
A little. Both formats are lossy, so the file is decoded and compressed a second time and the two sets of artefacts add up. At a high quality setting the difference is hard to see, but avoid repeated round trips between lossy formats.
Does extracting the audio re-encode it?
Only when the target codec differs from the one in the MP4. Where they match, the track is copied and the result is identical to the audio inside the video. Converting to a different codec means one extra generation of lossy compression.
Is my MP4 file uploaded anywhere?
No. The whole thing runs inside the browser tab you already have open. Your MP4 is read straight from your own disk, converted on your machine and handed back as an AAC. Nothing is sent anywhere, nothing is stored and there is no account.
Is there a file size limit?
There is no server-side limit because no server sees the file. The real ceiling is your device memory, since the input and the output both have to fit in the tab. A few hundred megabytes is usually fine on a desktop machine and considerably less on a phone.
Can I convert several MP4 files at once?
Yes. Add as many as you like and they are processed one after another, then offered as separate AAC downloads or as a single ZIP. Speed depends on your own processor rather than on a queue.
Does the converter work offline?
Yes, after the page has loaded once. The engine is cached by the browser, so you can disconnect, reload and keep converting. That falls out of doing the work locally rather than being a separate mode you switch on.