I found this video that use a trick of specifying the domain with www, but when I do that since I did it before without the www it reuse the CNAME of the previous domain (without www) at the root level. Should I just wait and try again ? If yes how long?

Here is the link: https://www.youtube.com/watch?v=tpW4jw4Uuuk

I switched to Cloudflare at the end, but still got a warning for the cname:

It works actually thanks

It no longer works I'm totally confused

Hi,

DNS propagation can take up to 72 hours to be effective. In most case it will never be longer than a few hours but it all depends on the DNS servers used. For example, if you edit your DNS zone on Cloudflare, someone using Cloudflare DNS will probably see the changes almost immediately but someone using Google DNS may have to wait a few hours.

Furthermore, Cloudflare is proxying all your A, AAAA or CNAME records by default (There is the little orange cloud next to your record saying "Proxied"). In that case, Railway detects the proxy by checking on Cloudflare IPs but leaves a warning (You can see on your screenshot "Cloudflare Proxy Detected"). It just means that they detected your subdomain was proxied so they are unable to check it's routed to your domain but it would still works very well

If you really wan't to get rid of this warning and let Railway manage TLS certificates for you instead of Cloudflare, you can simply uncheck the "Proxy" box by editing your CNAME record. Keep in mind that your traffic will no longer go through Cloudflare infrastructure and you will not benefit from many of their features (WAF, Caching, Content optimization, etc...). It will become a simple CNAME record.

Hope that helps !