DNS usage

[Marauder2003]

The DNS in my router is set to 1.1.1.1 and 9.9.9.9. The Windows PC internet connection also has DNS settings. Which is actually used when connecting to the internet from the PC?

The iPad is set to automatic and the DNS server is set to my router. But this brings up a question. What if I am not using my router when out and about using public wifi? Should I set the iPad to manual and put in my choices for DNS?

[ocabj]

DHCP leases should always include the DNS server to use. Your router can serve out either it's own IP address to the client as the DNS server to use or external DNS (e.g., 1.1.1.1). Just configure the client to use the DNS configuration from the DHCP server (or in this case, router). Thus, when you take that device elsewhere that uses DHCP, it will get whatever DNS configuration is part of that lease.

[ldsnet]

Your network provider should include the DNS server in the DHCP info when your computer gets its address. But I can warn, not all DNS servers are equal! I have issues with my spectrum server from time to time, and ATT with my phone is marginally better.
Running my VPN bypasses both of the servers and solves the name resolution and page load delay issues.
if you need to manually assign, 8.8.8.8 and 8.8.4.4 are good choices, they are maintained by google ... but have no connection to their search engine.

[opticsauthority]

Your PC usually prioritizes the DNS settings defined on the device itself over those set on the router. On your iPad, automatic is fine for most cases, but if you want more control while on public wifi, you can set manual DNS like on your PC. Public DNS options like Google (8.8.8.8, 8.8.4.4) are popular choices.