"Use unique domain" causes a redirect back to gitlab.io subdomain when using a custom domain
Summary
I tried to set up GitLab Pages for the first time and was very confused when my custom domain kept redirecting back to a gitlab.io subdomain. A team member suggested I move the project to a group and see what happened and I noticed that the subdomain stayed the same. That's when I realized this problem might be related to the "Use unique domain" setting, which had been checked by default when I started the project. When I unchecked that, the server stopped redirecting away from my custom domain.
Steps to reproduce
- Create a new public project and enable GitLab Pages, leaving the default "Use unique domain" checked.
- Add a top-level custom domain. I used an A record but it also seems to happen with an ALIAS record. I haven't tried this with a subdomain yet.
- Wait for domain verification, DNS, Let's Encrypt, etc to finish.
- Visit the custom domain - you'll be redirected back to the unique subdomain on gitlab.io.
Example Project
Repository: https://gitlab.com/horrorcheck/test-unique-domain-redirect
Unique gitlab.io subdomain: https://test-unique-domain-redirect-horrorcheck-daa2194395c329ab51c55e6.gitlab.io/
Custom domain: https://daydrea.me
What is the current bug behavior?
Custom domains with the default "Use unique domain" setting still enabled redirect from the custom domain to the unique subdomain, but the documentation doesn't explain that you need to uncheck that setting to avoid this.
What is the expected correct behavior?
Either the "Use unique domain" and "Custom domain" settings should be mutually exclusive, or there should be documentation explaining what happens when you attempt to use both and how to avoid that.
Output of checks
This bug happens on GitLab.com