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, new allocations were exhausted in 2011.
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 (city/district level)
- Identifying your home address requires a legal disclosure request to the ISP
- ISPs do not disclose personal information without a court order
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, it only reveals city-level location, 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.