Convert AAC to MP3
Turn .aac files into MP3s for the players and forms that still refuse AAC, without uploading them.
- Nothing is uploaded
- Works offline after first use
- Open source
- No sign-up, no watermark. The limit is your device’s memory (phones hold less).
Convert raw AAC audio files to MP3 in your browser, for car stereos, old players and upload forms. It is free, needs no account and adds no watermark, and your files are not uploaded: everything runs in your browser on your device. The limit is your device’s memory, which is smaller on a phone, and after your first run the page works offline.
Your iPhone may take a few seconds to prepare the video first, longer if it's stored in iCloud.
Done
Open the network tab. Your files never appear in it.
Add files and run the tool to see every request this tab makes.
Your files are processed on this device and never sent to a server. Reload the page to clear everything from memory.
A file ending in .aac is bare AAC audio in ADTS frames, with no MP4 wrapper around it. Android call and voice recorders, some dashcams and body cameras, radio stream captures, Bluetooth and TV recordings, and a few podcast tools save this way. AAC is a better codec than MP3, but plenty of car stereos, older MP3 players, church and school sound desks, and website upload forms still only accept MP3.
This page decodes the AAC with your browser’s own decoder and encodes an MP3 with the LAME encoder running in the page. Because AAC does more with fewer bits, pick an MP3 bitrate at or a little above the source: a 128 kbps AAC sounds closest to its original as a 160 or 192 kbps MP3. The page opens at 192 kbps.
Raw AAC files have no duration field in a header, so some players show a wrong length or cannot seek in them. The MP3 written here is a plain constant-bitrate file, and every player reports its length correctly and seeks straight to any point.
If your file ends in .m4a instead, it is the same AAC audio inside an MP4 container, and converts the same way here or on the M4A to MP3 page.
How it works
- Drop one or more AAC files, or tap to pick them.
- Keep 192 kbps, or match your source: 128 kbps for speech, 256 kbps for high-quality music.
- Convert. The MP3 downloads; several come as a zip.
In your browser, not on a server
Your browser decodes the sound track with the same audio decoders it uses to play media on any website (AAC for MP4, MOV and M4A; Opus or Vorbis for WebM; FLAC, WAV and MP3). The samples are resampled to 44.1 kHz and handed to LAME, the reference MP3 encoder, compiled to WebAssembly and served by this site. WAV files are written directly by a few lines of code in the page. Everything happens in memory in your tab.
Compared with upload-based tools: Online converters upload the whole video just to keep its sound, cap free files at a few hundred megabytes, and make you wait in a queue. Home videos, lectures and voice memos are personal. Here the file never leaves your device, so a 1 GB video converts as fast as your computer can read it, and the limit is your device’s memory (phones hold less).
Verify it yourself. Give the page a short while after your first run to save itself for offline use, then turn off Wi-Fi or switch to airplane mode and run the tool again. Or open your browser's developer tools (F12, or Cmd-Option-I on a Mac), pick the Network tab, and watch it while you convert. The panel above does the same count for you.
Questions
Is AAC better than MP3?
At the same bitrate AAC usually sounds a bit better. Convert only because something needs an MP3, and use a bitrate at least as high as the AAC’s to avoid an audible step down.
What is the difference between .aac and .m4a?
Both hold AAC audio. An .m4a wraps it in an MP4 container with a header, tags and cover art; an .aac is the raw stream. Both convert here.
Why does my AAC file show the wrong length?
Raw AAC has no header giving the total duration, so players estimate it. The MP3 you get here has a fixed bitrate, so its length is always shown correctly.
Which bitrate should I choose for an AAC file?
Match or exceed the AAC's own bitrate: most AAC files from phones, radio streams and camcorders are 96 to 256 kbps, and converting to a lower MP3 bitrate adds a second loss on top of the first. 192 kbps is a safe choice for music, 128 kbps for speech.
Is the file uploaded anywhere?
No. There is no server in this process. The page is a static file and the work is done by code running inside your browser tab. Give the page a short while after your first run to save itself for offline use; then you can turn off Wi-Fi and it still works.
More video and audio tools
Video to MP3
Pull the sound out of a video, or turn any audio file into an MP3. Your files are converted on this device and never uploaded.
Merge videos
Combine clips into a single video, in the order you choose. Done on this device, never uploaded.
Add audio to video
Put music or a voice-over on a video, or replace its sound. The picture is copied as it is, and nothing is uploaded.
Reverse video
Make a clip play backwards, for a rewind effect, a boomerang or a laugh. Done on this device, never uploaded.
Other conversions
Guides
- How to convert a video to MP3This is different from muting a video: you want the sound saved as its own file. Most devices have no built-in way to do that.
- Is Convertio safe?Convertio is a well-known converter with a published deletion policy. For private files, the safer choice is a converter that never receives them.
- Is Zamzar safe?Zamzar is one of the oldest online converters. Its storage window is longer than most, which is the detail worth knowing.
- A free CloudConvert alternative for everyday filesCloudConvert measures its free tier in credits tied to conversion time, not files, which makes it hard to predict when you will hit the limit. Here is an alternative with nothing to meter.
- A free Convertio alternative with no file size capConvertio's free plan caps both file size and how many conversions you get per day. Here is an alternative with no such ceiling.