IP Address
An IP address is a unique numeric identifier assigned to every device connected to a computer network that uses the Internet Protocol for communication.
§ 1 Definition
An IP address (Internet Protocol address) is how devices find each other on a network. Every device connected to the internet gets an IP address. There are two versions: IPv4 (32-bit, written as four numbers separated by dots, like `192.168.1.1`) and IPv6 (128-bit, written as eight hexadecimal groups separated by colons, like `2001:0db8:85a3::8a2e:0370:7334`). IPv4 supports roughly 4.3 billion addresses. The world ran out of unallocated IPv4 blocks years ago. IPv6 is the solution, with 340 undecillion addresses (enough for every grain of sand on Earth to have its own). Despite this, IPv6 adoption remains frustratingly slow. Your IP address reveals your approximate geographic location and your internet service provider. That is why VPNs exist.
§ 2 Public vs. private IPs
Routers assign private IP addresses within a local network (ranges like `192.168.x.x`, `10.x.x.x`, `172.16.x.x`). These are not routable on the public internet. The router has one public IP that all devices share via Network Address Translation (NAT). When you check "what is my IP" online, you see your public IP, not your laptop's private one.
§ 3 Static vs. dynamic
ISPs typically assign dynamic IP addresses that change periodically. Static IP addresses remain fixed and are used for servers, VPNs, and services that need a consistent address. Static IPs usually cost extra.
§ 4 Common misconception
Your IP address is not your identity. It identifies your network connection, not you as a person. Multiple people can share the same IP (NAT). Your IP changes when you connect through a different network. Law enforcement needs more than an IP address to identify an individual.
§ 5 Note
§ 6 In code
```bash
# Check your public IP from the terminal
curl ifconfig.me
# Or
curl ipinfo.io/ip
```§ 7 Common questions
- Q. What is the difference between IPv4 and IPv6?
- A. IPv4 is 32-bit with 4.3 billion addresses. IPv6 is 128-bit with an astronomically larger address space and built-in security features.
- Q. Can two devices have the same IP address?
- A. Not on the same network. But private IPs (like 192.168.1.1) are reused across millions of local networks.
- IP addresses uniquely identify devices on a network.
- IPv4 exhaustion is real. IPv6 is the long-term solution.
- Public IPs are shared through NAT. Private IPs are not internet-routable.
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Get in touchAn IP address is a unique numeric identifier assigned to every device connected to a computer network that uses the Internet Protocol for communication.
Category: Web Development (also: Infrastructure)
Author: Atomic Glue Team
## Definition
An IP address (Internet Protocol address) is how devices find each other on a network. Every device connected to the internet gets an IP address. There are two versions: IPv4 (32-bit, written as four numbers separated by dots, like `192.168.1.1`) and IPv6 (128-bit, written as eight hexadecimal groups separated by colons, like `2001:0db8:85a3::8a2e:0370:7334`). IPv4 supports roughly 4.3 billion addresses. The world ran out of unallocated IPv4 blocks years ago. IPv6 is the solution, with 340 undecillion addresses (enough for every grain of sand on Earth to have its own). Despite this, IPv6 adoption remains frustratingly slow. Your IP address reveals your approximate geographic location and your internet service provider. That is why VPNs exist.
## Public vs. private IPs
Routers assign private IP addresses within a local network (ranges like `192.168.x.x`, `10.x.x.x`, `172.16.x.x`). These are not routable on the public internet. The router has one public IP that all devices share via Network Address Translation (NAT). When you check "what is my IP" online, you see your public IP, not your laptop's private one.
## Static vs. dynamic
ISPs typically assign dynamic IP addresses that change periodically. Static IP addresses remain fixed and are used for servers, VPNs, and services that need a consistent address. Static IPs usually cost extra.
## Common misconception
Your IP address is not your identity. It identifies your network connection, not you as a person. Multiple people can share the same IP (NAT). Your IP changes when you connect through a different network. Law enforcement needs more than an IP address to identify an individual.
## Note
IPv4 addresses displayed in your server logs are not always the visitor's true IP. CDNs, proxies, and VPNs all change the source address. Use the `X-Forwarded-For` header to get the original client IP, but be aware it can be spoofed.
## In code
## Common questions Q: What is the difference between IPv4 and IPv6? A: IPv4 is 32-bit with 4.3 billion addresses. IPv6 is 128-bit with an astronomically larger address space and built-in security features. Q: Can two devices have the same IP address? A: Not on the same network. But private IPs (like 192.168.1.1) are reused across millions of local networks.
## Key takeaways
- IP addresses uniquely identify devices on a network.
- IPv4 exhaustion is real. IPv6 is the long-term solution.
- Public IPs are shared through NAT. Private IPs are not internet-routable.
## Related entries
- [DNS](atomicglue.co/glossary/dns)
- [URL](atomicglue.co/glossary/url)
- [HTTP](atomicglue.co/glossary/http)
- [TLS/SSL](atomicglue.co/glossary/tls-ssl)
Last updated June 2026. Permalink: atomicglue.co/glossary/ip-address