What AAC is and why it exists
AAC stands for Advanced Audio Coding. It is a lossy format, meaning it makes files small by removing parts of the sound that people are least likely to notice. It was designed as a successor to MP3 and generally reaches similar quality at a smaller size, or better quality at the same size.
You meet AAC all the time without noticing: it is common on Apple devices, in streaming services, and inside many video files. The standalone files this tool produces use the .aac extension and the aac encoder.
When you would convert to AAC
The usual reason is size. If you have a WAV or FLAC recording that is too big to email or upload, converting it to AAC can shrink it considerably while keeping it listenable. Another reason is compatibility with a specific player, phone, or workflow that expects AAC.
AAC is lossy, so it is not the format for masters or files you plan to keep editing. Every lossy re-encode removes a little more information. Keep your original lossless file and treat the AAC as a copy for listening or sharing. If you need the format that plays on the widest range of older equipment, the MP3 Converter is the safer pick.
How to convert audio to AAC with this tool
- Drop an audio file onto the upload area, or click it to browse.
- Check the file name and size shown, then click Run. This tool has no bitrate or quality setting, so there is nothing else to adjust.
- On first use, the page downloads the ffmpeg engine (roughly 30MB). A progress bar shows while it works.
- Play the result in the audio player that appears to check it sounds right.
- Click Download. The saved name is your original file name plus "-convert", ending in
.aac. - Choose Start over if you want to convert a different file.
The conversion runs inside your browser. Your file is not sent to a server.
Things to know before you rely on the result
The tool uses the encoder's default settings, so you cannot choose a target bitrate. If you need precise control over file size or quality, a desktop encoder will give you that.
The output is a raw AAC stream with an .aac extension, not an .m4a file. Most players handle it, but some Apple software prefers M4A, so test it on the device where it will be used. Raw AAC streams also carry little or no metadata, which means song titles and artwork from the source are unlikely to come along.
Very long files are processed in browser memory, so a big recording can be slow. If you get "Couldn't process this audio file.", try a shorter clip. To shorten a file first, use the Audio Cutter.