To sum up why TikTokDer is worth turn to account? If I can download the video using TikTok built-in functions itself why I need to use TikTok Downloader? Yes, you can use the TikTok default built-in functions.
But pay attention to few remarks: Each downloaded video will have watermark which includes TikTok logo and creators' nickname.
Or check «Resent downloads» folder if you use computer.
You don't need to install anything.
You just need TikTok video link to download a video.