Localhost

IPv4 network standards reserve the entire address block 127.0.0.0/8 (more than 16 million addresses) for loopback purposesA

• Address 127.0.0.1 is the standard address for IPv4 loopback traffic
• 127.0.0.1:8000 is the same as localhost:8000 is browser

Run via Terminal

Python3

$ python3 -m http.server 8000

Node.js, by default it picks a port (usually 3000)

$ npx serve

Php

$ php -S localhost:8000