MP3, not the video file
A video download is an MP4, picture and sound together. An MP3 is the audio file alone, which is what you want when you need the sound without the video frames. TikDownTok shows that audio row when the post exposes one.
Most of these files are MP3. A few posts offer M4A instead. The format is written on the button, so you know which one you are saving. The file name ends in .mp3 or .m4a to match.
Related: Audio downloader · Save the video as MP4
When there is no MP3
Some posts do not publish a separate audio file. You may still see video options. That is a limit of the source, not a missing button. There is no extra step that extracts audio on this site if the post did not include an audio URL.
Music on TikTok is often owned by someone else. Saving an MP3 does not license the song. Get permission before you reuse it in your own video or anywhere public.
Find the file after it downloads
Browsers treat an MP3 like any other download. On a computer, look in Downloads or the browser’s download list. On a phone, look in the Files app or the download notification. Then open it in the music app you already use.
If the button expires, paste the link again. Do not reuse an old download address from hours ago.
Related: Computer · iPhone and iPad