What is a nAT?
In one sentence: How a router lets every device at home share one public internet address, swapping addresses on the way out and back.
A little more
NAT, short for network address translation, is how every device in a home can share one public internet address. When your tablet asks a website for a page, the router swaps the tablet's private address for the home's public one on the way out, and remembers to pass the answer back to the tablet when it arrives.
Because the router only knows where to send answers to conversations someone inside started, a stranger on the internet cannot start a conversation with a device at home. That is good for safety, and it is also why hosting a game server at home needs a port-forward rule. Some internet providers add a second NAT of their own, called carrier-grade NAT, so several homes share one address.
See it in action
- 1What happens when you open a web page?Follow one click from your keyboard to a server and back: DNS, the padlock handshake, HTTP, tunnels and painting the page.6 min · interactive
- 2Anatomy of a web addressPaste any web address and see it taken apart, colour by colour: scheme, host, port, path, query and the fragment that never reaches the server.5 min · interactive
- BonusHow does the router know which device asked?Your home has one internet address but lots of screens.7 min · interactive
Do it for real
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