Cloudflare DNS

I find DNS confusing, so I'm writing this down for future reference.

I just pointed notebook.samfeldstein.xyz to this site. To do that, you first add notebook.samfeldstein.xyz to the notebook's Cloudflare Pages site as a custom domain. Then you add a corresponding CNAME record to samfeldstein.xyz.

www.problems.fml

For whatever reason, adding a CNAME that points www. to samfeldstein.xyz wasn't working. What's extra-weird is that the CNAME method works fine for my other domains (eg samfeldstein.net). But I added 301 redirect that does the same thing and it works fine.

All other domains are redirecting to my main site, and seem to be working.