Convert MP4 to AAC
Free online converter for MP4 files. Efficient successor to MP3 used in broadcast and streaming. Nothing to install, no watermark, and every file is deleted automatically.
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Upload a MP4 file to convert it to AAC. Up to 3 files at once, 100 MB each.
Free · up to 3 files · 100 MB each · files deleted automatically after 1 hour.
About MP4 and AAC
MP4 .mp4
The universal video container, normally holding H.264 video and AAC audio. If a device plays video at all, it plays MP4.
Good for
- Plays on effectively every device, browser and editor
- Excellent compression at high quality
- Streams well, and seeks quickly
Trade-offs
- H.264 carries patent licensing obligations
- Lossy — quality drops each time it is re-encoded
- Less flexible than MKV for subtitles and multiple tracks
video/mp4
AAC .aac
MP3's designated successor, and the default in the Apple ecosystem and most streaming services. Better sound than MP3 at the same bitrate.
Good for
- Noticeably better than MP3 at equal bitrates
- The default across Apple devices and most streaming
- Handles multichannel audio properly
Trade-offs
- Lossy
- Patent licensing is more involved than Opus or Vorbis
audio/aac
MP4 and AAC side by side
| MP4 | AAC | |
|---|---|---|
| Compression | Lossy (usually H.264) | Lossy |
| Transparency | No | n/a |
| Typically used for | Everything — the safe default for video | Streaming, Apple devices, video soundtracks |
What changes when you convert MP4 to AAC
Only the sound is kept
This takes the audio track out of the MP4 and writes it as AAC. The picture is discarded entirely, and no conversion back will return it — keep the MP4 if you still need the video.
This is a re-encode, not a repackage
Some tools can move a stream into a different container untouched when the codecs happen to line up. We do not — every job here is decoded and encoded again, so the conversion takes time in proportion to the length of the file and costs a small amount of quality even where a repackage would have been possible. In exchange the output is predictable: it plays everywhere, rather than inheriting whatever the source happened to contain.
What your AAC will contain
The output is AAC — at 192 kbps, written as a raw ADTS stream rather than wrapped in a container. AAC is meaningfully better than MP3 at the same bitrate, which is why it became the default for streaming and broadcast. If you want tags and artwork to travel with it, choose M4A instead — the same audio in a container that has somewhere to put them.
Other MP4 conversions
Other ways to get AAC
Worth reading next
MP4, MOV and MKV are not really video formats
The extension on a video file tells you far less about it than most people assume. Understanding the difference between a container and a codec explains almost every confusing thing about video conversion.
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What 192 kbps actually means, and when you need more
Bitrate is the single dial that decides how big an audio file is and how good it sounds. Here is what the numbers mean, why they are not comparable between codecs, and where the real thresholds sit.
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