Connection essentials

IPv4 vs IPv6

IPv4 and IPv6 are two versions of Internet Protocol. IPv4 addresses use four decimal groups, such as 203.0.113.42. IPv6 uses hexadecimal groups and colons, such as 2001:db8::42. These examples are reserved for documentation.

Why there are two

IPv4 has a limited address space. IPv6 provides a vastly larger one. Many networks support both, a configuration called dual-stack. A browser can choose one family for a particular request, so the address shown on a page does not by itself prove whether the other family works.

How connection tests work

Separate requests to IPv4-only and IPv6-only destinations can check whether each address family is reachable. A successful request to one destination does not prove that all destinations are reachable.

Understanding a failed test

A timeout can be caused by your network, DNS, VPN, browser extension, firewall or the test endpoint. “Not detected” means that a test did not complete successfully. It is not a diagnosis of the whole network.