Coub serves its media as MP4, and that is exactly what you keep. The container is passed through rather than rebuilt, so there is no generation loss between what Coub stored and what ends up in your downloads folder. Coub is handled by the media route, which reads the site's own rendition list before choosing anything. No credentials are involved anywhere in this path — neither yours nor ours.
Two ways in: the box above, or prefix the Coub URL you are already looking at with tikt.com/:
tikt.com/https://www.example.com/path/to/media
What you actually have to do
1. Copy the Coub link
Use the address bar or the platform's own share button — both give a URL the extractor recognises. Point it at the single item you want, not the page around it.
2. Let it read the renditions
Paste the URL above. The extractor asks Coub which renditions exist for that item and picks the best progressive one rather than assuming a quality.
3. Save what comes back
The file arrives in the container Coub served it in, and the extractor does not rebuild it — so what you end up with is what the uploader encoded, for better or worse.