Use whitelist only?

Is it possible to have pi-hole double as a domain whitelist for parental controls?

Can you elaborate on what you're looking for? You can already whitelist domains.

It would be cool if there was a simple mode to toggle "whitelist only" --- this would only resolve the domains on the whitelist and sinkhole everything else.

I imagine using this in limited network environments, particularly guest, kiosk, or student networks where there is a very short list (i.e. < 20) of domains that should be accessible.

Thank you!

UPDATE

There are quite a few places around the internet where other folks are asking for/seeking the same thing, here are just a couple examples:

Thank you!

Try blocking . as a wildcard.