About this tool
This decodes and re-encodes raw .aac (ADTS) audio files to MP3 using ffmpeg.wasm — a full build of the real ffmpeg audio/video engine compiled to WebAssembly and loaded straight into your browser. Every file in the queue is processed with the same bitrate, sample rate, channel, trim, volume and fade settings above; nothing is ever sent to a server.
Is converting AAC to MP3 actually worth it?
At the same bitrate, AAC generally sounds a bit better than MP3 — it's a newer, more efficient codec. So converting to MP3 usually isn't about quality, it's about compatibility: MP3 is still the most universally supported audio format across old hardware, car stereos, and software that never added AAC support. Also note this is a lossy-to-lossy re-encode, so there's a small additional quality cost versus the original AAC — pick as high a bitrate as your use case allows if quality matters.
My file is .m4a, not .aac — will this work?
Not directly. A raw .aac file is a bare ADTS audio stream, while .m4a is an AAC audio stream wrapped inside an MP4 container — they're different file structures even though both hold AAC audio. This tool is built and validated specifically for raw .aac files. If your file is .m4a, use the separate M4A to MP3 Converter tool instead.
Is my audio uploaded anywhere during conversion?
No. ffmpeg.wasm runs the entire decode/encode pipeline inside your browser via WebAssembly — your files never leave your device. The engine itself (roughly 25MB) does need to download the first time you use any converter tool on this site, then it's cached by your browser.