Convert Advanced Audio Coding (.aac) to MPEG-4 Part 14 (.mp4) online for free. Fast, secure audio conversion with no watermarks or registration.
Upload your .aac file by dragging it into the upload area or clicking to browse.
Choose your output settings. The default settings work great for most files.
Click Convert and download your .mp4 file when it's ready.
AAC is the standard audio codec inside MP4 containers — they are natural partners defined together in the MPEG-4 specification. Converting a standalone AAC file to MP4 wraps the audio stream in the full MPEG-4 Part 14 container, adding proper metadata support, streaming headers, and compatibility with every video player, web browser, and mobile device on the planet. MP4 is the most universally supported media container in existence.
Raw AAC files (ADTS format) lack metadata, streaming optimization, and consistent player support. MP4 containers are recognized by literally every modern media device and platform. Wrapping AAC in MP4 enables web streaming with byte-range requests, proper metadata display in all players, and the ability to later mux video into the same container. Web browsers play MP4 audio natively via the HTML5 audio element.
FFmpeg copies the AAC bitstream into an MP4 (MPEG-4 Part 14) container using stream copy. The moov atom is placed at the file start (faststart) for streaming compatibility. MP4 adds proper metadata atoms (udta), sample tables for seeking, and optional chapter markers. The process is a pure remux — no transcoding occurs.
Bit-for-bit identical to the source. MP4 is a container change only — the AAC audio data is not modified in any way.
| Device | AAC | MP4 |
|---|---|---|
| Windows PC | Partial | Native |
| macOS | Native | Native |
| iPhone/iPad | Native | Native |
| Android | Partial | Native |
| Linux | Partial | Native |
| Web Browser | No |
Resolution: N/A
Bitrate: 320 kbps
OGG Vorbis preferred
Resolution: N/A
Bitrate: 256 kbps
AAC format required
Resolution: N/A
Bitrate: 128 kbps
Lossless FLAC/WAV for best quality
Resolution: N/A
Bitrate: 128 kbps
MP3 mono for spoken word
AAC to MP4 is the most pragmatic container conversion. MP4 is supported everywhere — browsers, phones, smart TVs, game consoles, car stereos — making it the safest choice for audio distribution.
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| Native |
| Egenskap | AAC | MP4 |
|---|---|---|
| Fullt navn | Advanced Audio Coding | MPEG-4 Part 14 |
| Filendelse | .aac | .mp4 |
| Best egnet for | Superior to MP3 | Universal compatibility |