When you see a domain like rr13---sn-pmcg-bg0z.googlevideo.com, it's natural to wonder if something suspicious is going on. The good news is that this is simply a YouTube CDN server, owned and operated by Google. It's not a third-party website trying to trick you.
The site returns a 404 error because the server is designed to serve video content, not a landing page. That's normal for this kind of infrastructure. The SSL certificate is valid and issued by Google Trust Services, the site loads cleanly on all security checks, and there's no history of abuse. If you see this domain in a link or embedded video, you can trust that the content is coming from Google's own network.
Is rr13---sn-pmcg-bg0z.googlevideo.com safe? Yes, it's as safe as any other Google endpoint. Just keep in mind that it's not a website you browse — it's a server that delivers streaming data. As long as you're on a legitimate Google service, there's no reason to be concerned.