Today I learned the hard way that WordPress multisite doesn’t quite support domain mapping out of the box the way I expect it to.
I’m working on a website-as-a-service product called ToothPress (more on that at some point in the future). On a paid plan, ToothPress customers will be able to map their custom domain. My dad is my first beta user, so I changed his domain from milwaukiefamilydentistry.toothpress.com to milwaukiefamilydentistry.com:
Then, I went to log into his dashboard:
Uh oh, what’s going on?!
As it turns out, WordPress doesn’t magically handle setting the correct COOKIE_DOMAIN. You’ll need to take care of this yourself: