AAC (Advanced Audio Coding) is a lossy audio compression format standardized in 1997 as the successor to MP3. It's the default audio format used by Apple across all its devices and platforms, and is the audio codec embedded inside most MP4 video files. YouTube, Spotify, and most major streaming services use AAC for audio delivery.
AAC files are typically saved with the .aac or .m4a extension. The .m4a extension (MPEG-4 Audio) is the same codec wrapped in an MP4 container, which is what Apple uses for iTunes and Apple Music purchases.
At the same bitrate, AAC generally produces better audio quality than MP3. A 128 kbps AAC file typically sounds comparable to a 192 kbps MP3. The trade-off is compatibility: MP3 works on virtually every device ever made, while AAC - though widely supported today - may not play on older or obscure hardware.
Like MP3, AAC is a lossy format - it permanently removes some audio data during encoding. WAV is lossless and preserves audio exactly. For professional recording, archiving, or further audio editing, WAV is the right choice. For distribution and playback, AAC is efficient and high quality.
AAC is the audio track inside virtually every MP4 video file, every iTunes purchase, and most podcast and streaming audio. It's also the recording format used by iPhone voice memos and many video conferencing apps.
You can convert MOV to MP4 or extract audio from any video as AAC directly in your browser - no software to install, no upload required.