TikTok is a deceptive platform from a downloading standpoint: it looks simple because the videos are short and the URLs are clean, but the actual playback pipeline does a surprising amount of work in the background. Every play_addr URL is signed against the requesting session, expires within minutes, and is delivered differently depending on whether the request came from a logged-in in-app session, an unauthenticated web session, or a third-party scraper. The variant TikTok exposes — watermarked, clean, low-bitrate, full-bitrate — depends on which of those contexts the request looks like. This is why two different downloaders can return two different versions of “the same” TikTok and neither is wrong, just operating in different contexts.
The practical consequence is that the file has to be inspected rather than assumed. Nothing in the URL or the save dialog tells you which variant arrived, so the only reliable check is opening the result: look at its dimensions, listen for the audio, and see whether an overlay is present. If you own the upload, your own original in the TikTok app is the better source than any re-capture of the published version.
Expiry is the second recurring surprise. A signed address is valid for minutes and only for the request that obtained it, which makes the copy-the-URL-and-paste-it-elsewhere approach fail in a specific, confusing way: it works if you are quick and fails a few minutes later with a 403, so people conclude the tool is unreliable rather than that the link had a deadline. Working from the page while the video is actually playing avoids the whole class of problem.
Access restrictions on TikTok are stricter than they first appear. A private account requires an approved follow. A friends-only video requires a mutual follow, which is a different and narrower condition. Both are enforced before the video is ever sent to your session, so neither is something a downloader can be configured around — the fix is the relationship on TikTok, and having it still does not settle whether you may keep a copy.
One last distinction that causes real confusion: TikTok and Douyin are not the same service. They share an owner but run separate apps, separate libraries and separate URL schemes, so a link from douyin.com is not a TikTok link and results on one say nothing about the other. Check the hostname before concluding anything about support.