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Glossary

AAC Audio

Also known as: Advanced Audio Coding, .aac

AAC was standardized in 1997 and is the audio component of the MPEG-4 standard. At a typical web bitrate of 128 kbps, AAC produces audio that's transparent (indistinguishable from CD quality) for most listeners — a quality tier that requires roughly 192 kbps in MP3. This compression efficiency is why every modern video codec ecosystem standardized on AAC for audio.

When you download a video from a social platform, the audio inside the MP4 is almost always AAC at 96-128 kbps mono or 128-192 kbps stereo. Tools that extract audio (like DropZap's video-to-MP3 mode) typically transcode the AAC track to MP3 because MP3 has slightly broader compatibility with older devices and software, even though MP3 at the same bitrate is lower quality.

The .aac file extension exists but is rare in practice — when AAC is extracted from a video, the file is almost always re-wrapped as either an .m4a (the standard Apple/iTunes container for AAC audio) or transcoded to .mp3.

Related terms

MP4
MP4 (MPEG-4 Part 14) is a digital container format that holds video, audio, subtitles, and metadata in a single file. It is the dominant video format on the modern internet — TikTok, Instagram, YouTube, X / Twitter, Facebook, and Reddit all serve videos as MP4 internally.
H.264
H.264 (also called AVC, Advanced Video Coding) is the most widely used video compression codec on the internet. It compresses raw video into a much smaller file while preserving high visual quality, and it is the codec inside virtually every MP4 file served by TikTok, Instagram, YouTube, Facebook, X / Twitter, and Reddit.
Bitrate
Bitrate is the amount of data used to encode each second of video, measured in kilobits per second (kbps) or megabits per second (Mbps). Higher bitrate means more data per second, which means better visual quality but larger file size. At the same resolution, a higher-bitrate video looks substantially better than a lower-bitrate one.