Browser edition: files stay on your device. Up to 100 MB total and 10 minutes. First use downloads a 32 MB engine. Some formats depend on codec support. Public-link downloading is not ready on this free deployment.
Convert MP4 to AAC
Convert MP4 to AAC online for free. Extract the audio track at the bitrate you choose.
How to convert MP4 to AAC
- Add your fileDrop it on the page, choose it from your device, or paste it with Ctrl+V.
- ConvertAdjust settings if you like, then press the button. You'll see live progress.
- Browser processing uses original files on your device. Public-link downloading is unavailable.
What happens to your file
MP4 files are common for sharing, uploading to social networks, playing on any device, but not every app or device opens them. AAC is ideal for streaming, video soundtracks, mobile audio. Spool converts MP4 to AAC with FFmpeg — real decoding and encoding, not a renamed file extension.
Audio only. Spool drops the video stream and keeps the soundtrack. Because MP4 audio is normally AAC, choosing AAC with default settings copies it as-is — no quality loss at all. Tags such as title and artist are carried over when present.
Settings
- Audio bitrate — 320 kbps · best, 256 kbps, 192 kbps · standard, 128 kbps · small, 96 kbps, 64 kbps · voice
- Channels — Original, Mono
- Sample rate — Original, 48 kHz, 44.1 kHz, 22 kHz
MP4 vs AAC
| MP4 | AAC | |
|---|---|---|
| Full name | MPEG-4 Part 14 | Advanced Audio Coding |
| Created by | ISO / MPEG, 2001 | MPEG, 1997 |
| Type | Video container | Lossy audio |
| Typical contents | H.264 or H.265 video with AAC audio | AAC (lossy), raw ADTS stream |
| Best for | sharing, uploading to social networks, playing on any device | streaming, video soundtracks, mobile audio |
| Strength | Plays everywhere, including iPhone, Android, Windows and macOS | Higher quality than MP3 at equal bitrate |
| Weakness | Lossy: every re-encode loses a little quality | Raw .aac files have weaker tag support than M4A |
About MP4
- Type
- MPEG-4 Part 14
- Contains
- H.264 or H.265 video with AAC audio
- Use
- sharing, uploading to social networks, playing on any device
About AAC
- Type
- Advanced Audio Coding
- Contains
- AAC (lossy), raw ADTS stream
- Use
- streaming, video soundtracks, mobile audio
FAQ
What bitrate should I choose for AAC?
192 kbps is a good default for music. Choose 320 kbps for the best quality, 128 kbps for podcasts and voice, 64 kbps for small voice notes.
Can I convert several MP4 files at once?
Yes. Drop up to 10 files at a time — each one is converted in parallel and you can download them individually or all at once.
Is there a file size limit?
Convert and edit files on your device. The browser edition accepts up to 100 MB total, media up to 10 minutes and video up to 4K. Codec availability and device memory can limit individual jobs.
Is this MP4 to AAC converter free and safe?
Yes. There are no pop-ups, redirects or fake download buttons, and no software to install. Files are transferred over HTTPS, processed in isolated job folders and deleted automatically.