What are the differences between `localhost` and `127.0.0.1`?

Differences between localhost and 127.0.0.1

1. Type
   • localhost is a hostname (like a domain name).
   • 127.0.0.1 is an IPv4 loopback address.
2. Resolution
   • localhost is resolved by the system (via the hosts file or DNS) to an IP address, usually 127.0.0.1 or ::1 (IPv6).
   • 127.0.0.1 directly points to the loopback network interface without requiring resolution.
3. Protocol Support
   • localhost can map to both IPv4 (127.0.0.1) and IPv6 (::1) depending on system configuration.
   • 127.0.0.1 always refers to IPv4 only.
4. Configurability
   • The mapping of localhost can be modified in the hosts file (/etc/hosts or C:\Windows\System32\drivers\etc\hosts).
   • 127.0.0.1 is fixed as the IPv4 loopback and cannot be changed.
5. Use Case
   • localhost is easier for humans to read/write and works in most configurations.
   • 127.0.0.1 is used when you specifically want the IPv4 loopback address.

Quick Summary:

• localhost = a hostname that resolves to a loopback IP (IPv4 or IPv6).
• 127.0.0.1 = the specific IPv4 loopback address.
  They usually behave the same, but differences matter with IPv6, custom host mappings or network configurations.

• localhost is a hostname that refers to your own computer.
• 127.0.0.1 is the IP address (IPv4 loopback address) that points to the same local machine.

 localhost is resolved to 127.0.0.1 (or ::1 for IPv6) via the system’s hosts file.
So, both mean “this computer” but:

• localhost : name
• 127.0.0.1 : address

In Simple Terms

• localhost is a name -> resolved to -> 127.0.0.1 (or ::1 in IPv6).
• 127.0.0.1 is the actual IP address used by the system’s loopback interface.

So, both mean “this computer”
but localhost is a name, while 127.0.0.1 is the address.

• localhost : a human-friendly name for your own computer.
• 127.0.0.1 : the numeric IP address of your computer’s loopback interface.

Both point to your machine, but localhost goes through name resolution, while 127.0.0.1 goes directly to the IP.