Explaining IP Addresses Using "Addresses"

The string of numbers displayed when you visit IP Check-san - that's your IP address. It's often said that "an IP address is like a street address on the internet," but let's explain it a bit more precisely and clearly.

Think of It Like the Postal System

When you send a letter, you write the "recipient's address" and the "sender's address" on the envelope. Internet communication works exactly the same way.

  • Your IP address = the sender's address. "Please deliver the reply here"
  • The website's IP address = the recipient's address. "Please deliver this request to this server"

When you access a website through your browser, your device sends a request saying "My IP address is 203.0.113.42. Please give me the page for google.com." Google's server then sends the page data back to 203.0.113.42.

Without an IP address, the server wouldn't know "who to send the reply to," and communication couldn't happen.

IPv4 and IPv6 - Two Address Systems

IPv4 (e.g., 203.0.113.42)

Designed in 1981, this format uses four numbers separated by dots. There are approximately 4.3 billion addresses from 0.0.0.0 to 255.255.255.255. However, with the explosive growth of devices worldwide, IANA's central pool ran dry in February 2011, and the regional registries ran out one after another through the 2010s (Europe's RIPE NCC made its last regular allocation in November 2019).

IPv6 (e.g., 2001:0db8:85a3::8a2e:0370:7334)

A new format designed to address IPv4 exhaustion. It provides approximately 340 undecillion addresses (340 trillion trillion trillion) - enough to assign an IP address to every grain of sand on Earth with plenty to spare.

An IP Address Is Not Your Home Address

A common misconception is that your home address can be identified from your IP address. This is normally not the case.

  • What can be determined from an IP address is the approximate location of your ISP's connection point - the country and region are almost always right, but whether it narrows down to your city depends on the connection, and it can be off by tens of kilometers
  • Identifying your home address requires a legal disclosure request to the ISP
  • ISPs hand over subscriber details only after a legal procedure, such as a court-backed disclosure request or a formal enquiry from law enforcement

An IP address reveals something like "an NTT Docomo user in Shibuya, Tokyo" - not "Taro Yamada at 1-2-3 Jingumae, Shibuya."

IP Addresses Change

For most home internet connections, IP addresses are not fixed but dynamically assigned by the ISP.

  • Restarting your router may change your IP address
  • Toggling airplane mode on and off may change your mobile network's IP address
  • Connecting to a cafe's Wi-Fi means you'll use that cafe's IP address
  • Using a VPN changes your visible IP address to the VPN server's address

Try visiting IP Check-san a few times to see if your IP address changes.

Summary

An IP address is an "address on the internet" needed to identify the destination and return address for communication. Unlike your home address, all it reveals is the rough position of your connection point, and individuals cannot be identified without legal procedures. Check your IP address on IP Check-san and see what information can be read from it.

Related Terms in This Article

IP Address A number that identifies devices on the internet. Used to specify communication destinations and return addresses. ISP The internet service provider that assigns your IP address. DNS The system that converts domain names to IP addresses, so humans don't have to memorize them. VPN When using a VPN, the IP address visible to websites changes to the VPN server's address.

Frequently Asked Questions

What is an IP address?

An IP address is a numerical label assigned to every device connected to the internet, functioning like a postal address for data. It tells the network where to send information, just as a mailing address tells the postal service where to deliver a letter.

Can my home address be found from my IP address?

No. An IP address typically reveals only the approximate location of your ISP's connection point, along with the ISP itself. The country and region are usually right, but whether it narrows down to your city depends on the connection, and it can be off by tens of kilometers. Law enforcement can obtain your identity from your ISP with a court order, but ordinary individuals and websites cannot determine your home address from your IP alone.

Does my IP address change?

Most home internet connections use dynamic IP addresses that change periodically. Restarting your router, toggling airplane mode on mobile, or simply waiting can result in a new IP. Some ISPs offer static IPs that do not change, typically for business accounts.