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URL-to-IP conversion means resolving a URL’s hostname through DNS to find one or more IP addresses. For example, a lookup uses the hostname in www.example.com; it does not translate the entire URL into a single address. You can check the hostname with a DNS lookup page or a command-line utility.
What URL-to-IP conversion means
When you visit a website by name, your device asks a DNS resolver for address records associated with the hostname. Google Public DNS describes DNS as the web’s “phone book”: a computer performs a DNS lookup when you visit a website (Google Public DNS).
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A URL may include a scheme, hostname, path, and other components. DNS resolves the hostname, such as www.example.com, rather than converting the URL’s full text. If the URL already contains a literal IP address, a hostname-to-address lookup for that host is not needed.
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How to look up a hostname’s IP address
Use a DNS lookup page
Enter the hostname and choose the address record type you want to inspect. Google’s DNS lookup documentation explains how to enter a domain and record type in its lookup interface (Google DNS lookup instructions).
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Use a command-line DNS utility
Query the hostname with a DNS utility and specify A for IPv4 or AAAA for IPv6 when you want to check a particular address family. Google’s troubleshooting documentation illustrates command-line queries and explains how to test a hostname URL alongside a fixed-IP URL (Google DNS troubleshooting).
What A and AAAA records show
- A records: provide IPv4 addresses for a hostname.
- AAAA records: provide IPv6 addresses for a hostname.
Some IPv6-only networks use DNS64 with a compatible NAT64 gateway. In that setting, a resolver can synthesize an AAAA answer for a destination that has only an IPv4 address; this is a network-specific behavior, not a general conversion rule (RFC 6147: DNS64).
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Why a hostname can return several IP addresses
A hostname can have more than one address record. The answers can also differ with the resolver queried and the current DNS state, so a lookup is a view of DNS at that time—not a guarantee that every visitor or application will receive the same address.
Why the IP address may not work in place of the URL
Finding an address does not mean that replacing the hostname with that address preserves all web behavior. For HTTPS, the hostname can still be needed during the TLS handshake: Google’s TLS documentation states that literal IPv4 and IPv6 addresses are not permitted in the TLS Server Name Indication (SNI) HostName field (RFC 6066: TLS extensions). A site may therefore fail or behave differently when reached by its IP instead of its hostname.
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Use DNS lookup results to troubleshoot
If a hostname fails to resolve, the problem may be with name resolution. Testing a known fixed-IP URL can help distinguish that from a broader connectivity problem: if the fixed-IP test also fails, the cause may lie elsewhere in the network path. This comparison is a diagnostic clue, not proof of a particular cause; Google’s troubleshooting guidance describes the hostname and fixed-IP test (Google DNS troubleshooting).
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