Internet Protocol is the addressing and delivery system that gets your data to the correct computer

When you send an email or load a website, your device breaks the message into small chunks called packets. Each packet needs a destination address, just like a letter needs a mailing address. Internet Protocol (IP) is the set of rules that assigns those addresses and tells routers how to move packets from your computer to the right destination computer, even if they take different paths along the way.

Without IP, your device would have no way to label where data should go or how to find it when it arrives. IP works alongside other protocols — like TCP, which makes sure packets arrive in order and nothing gets lost — but IP itself handles only one job: getting the packet to the right address.

Key Takeaways

  • Every device on the internet has an IP address, which is either assigned by your internet provider (for your home network) or by your router (for devices inside your home).
  • IP packets include the sender's address, the destination address, and the data itself, allowing routers to forward them toward their target without knowing the entire path in advance.
  • IPv4 addresses use four numbers separated by dots (like 192.168.1.1), while IPv6 addresses use a longer format to support the billions of devices now connecting to the internet.
  • Your router uses IP addresses to decide which direction to send each packet, checking a routing table that tells it which path leads toward the destination.

How IP addresses work as identifiers

An IP address is a unique number assigned to every device that connects to the internet. Think of it as a postal address for your computer. Your internet service provider assigns one IP address to your home network. Inside your home, your router assigns different IP addresses to each of your devices — your laptop, phone, tablet, and so on.

When you send data, your device includes both its own IP address (the sender) and the IP address of the destination (the computer you are trying to reach). Routers along the path read the destination address and decide where to send the packet next, moving it one step closer to its target. The sender's address is included so the destination computer knows where to send the reply.

IP addresses come in two formats. IPv4 addresses use four numbers from 0 to 255, separated by dots — for example, 192.168.1.5. IPv6 addresses use a longer format with letters and numbers, like 2001:0db8:85a3:0000:0000:8a2e:0370:7334. IPv6 was created because the world ran out of available IPv4 addresses as more devices connected to the internet. Your device may have both an IPv4 and an IPv6 address at the same time.

What happens inside an IP packet

When your device sends data across the internet, it wraps that data inside an IP packet. The packet is like an envelope with a label on it. The label includes the sender's IP address, the destination IP address, and instructions for how the packet should be handled. The actual data — your email message, a photo, a web page — sits inside.

The packet also includes a Time to Live (TTL) field, which is a counter that decreases by one each time the packet passes through a router. If the TTL reaches zero before the packet reaches its destination, the packet is discarded. This prevents packets from bouncing around the internet forever if something goes wrong with the routing.

Packets are usually small — typically between 1,500 and 65,000 bytes depending on the network. If your data is larger than that, your device breaks it into multiple packets, each with the same destination address but a different sequence number so the receiving computer can put them back together in the right order.

How routers use IP addresses to forward packets

A router is a device that reads the destination IP address on each packet and decides where to send it next. Your home router does this for devices inside your house. Internet backbone routers do this for packets traveling across the world. Every router has a routing table — a list of IP address ranges and the direction (or interface) to send them.

When a router receives a packet, it looks at the destination IP address and checks its routing table. The table might say "if the destination starts with 192.168, send it out the local network port" or "if the destination is anything else, send it to the next router." The router does not need to know the entire path from source to destination — it only needs to know the next hop. Each router along the way makes the same decision, and the packet gradually moves closer to its target.

This system is called hop-by-hop routing. It is efficient because no single router needs a complete map of the entire internet. Instead, routers share information about which networks they can reach, and each router builds its own routing table based on that information.

The difference between IP addresses and domain names

You do not type IP addresses into your browser. Instead, you type domain names like google.com or housing-basics.org. Your device needs to convert that domain name into an IP address before it can send packets to the right place. This conversion happens through the Domain Name System (DNS), which is a separate system that works alongside IP.

When you type a web address, your device sends a DNS query asking "what is the IP address for google.com?" A DNS server responds with the IP address. Your device then uses that IP address to send packets to Google's servers. If Google changes which server hosts its website, it updates the DNS record, and your device automatically gets the new IP address the next time you visit.

Public IP addresses versus private IP addresses

Your internet provider assigns your home network a public IP address — a number that is unique across the entire internet and visible to websites you visit. Websites can see your public IP address and use it to know roughly where you are located (usually at the city or region level, not your exact address).

Inside your home, your router assigns private IP addresses to your devices. These addresses are not visible to the outside internet. They follow a standard format: addresses starting with 10, 172.16 through 172.31, or 192.168. Millions of home networks use the same private IP addresses because they are only meaningful within that local network. Your router translates between private and public addresses, a process called Network Address Translation (NAT). When your laptop sends a packet to the internet, the router replaces the private address with the public address so the response knows where to come back to.

Why IP alone is not enough for reliable communication

IP gets packets to the right address, but it does not may provide they will arrive in order, arrive at all, or arrive without damage. If a packet is lost or corrupted, IP does not automatically resend it. This is where TCP (Transmission Control Protocol) comes in. TCP works on top of IP and adds reliability: it numbers packets, checks that they arrive in order, detects damage, and requests resends if something goes wrong.

For applications that do not need perfect reliability — like video calls or online games — a different protocol called UDP (User Datagram Protocol) works with IP instead. UDP is faster because it does not wait for confirmation that packets arrived, but it accepts that some packets might be lost. The choice between TCP and UDP depends on what matters more: speed or accuracy.

Frequently Asked Questions

Can someone see my IP address when I visit a website?

Yes. Websites see your public IP address in the same way a store sees the address on a check you write. They can use it to estimate your general location (usually city or region level) and to block traffic from certain countries or networks. They cannot see your exact home address or personal information just from the IP address alone.

What is the difference between IPv4 and IPv6?

IPv4 uses four numbers (like 192.168.1.1) and can create about 4 billion unique addresses. IPv6 uses a longer format and can create trillions of addresses. The internet is gradually switching to IPv6 because we ran out of available IPv4 addresses, but both still work together on most networks.

Why do I have a different IP address sometimes?

Your internet provider assigns your home network a public IP address, and that address can change when you restart your modem or router, or when your provider's lease on that address expires. Inside your home, your router assigns private addresses to your devices, and those usually stay the same unless you restart the device or the router.

Does a VPN change my IP address?

A VPN (Virtual Private Network) replaces your public IP address with the VPN provider's IP address. Websites see the VPN's address instead of yours. However, the VPN provider can still see your real IP address and your traffic, so choosing a trustworthy VPN provider matters if privacy is your goal.

Can two devices have the same IP address?

On the same network, no — your router prevents it. Across the entire internet, yes — millions of home networks use the same private addresses like 192.168.1.1. Public IP addresses are unique, but if two devices somehow end up with the same public address, packets get confused and communication breaks down.