Public vs Private IP Addresses: The Digital Passport System
Every device connecting to the internet requires an IP address—think of it as your digital passport. But not all IP addresses function the same way. Understanding the distinction between public and private IPs is essential for grasping how your devices communicate both locally and globally.
Key Insight:
Your devices actually use both types of IP addresses simultaneously—a private IP for local network communication and a public IP (shared with other devices on your network) for internet access.
Public IP Addresses: Your Gateway to the Internet
A public IP address serves as your network's identity on the global internet. It's the address that websites, online services, and other networks use to communicate with your network.
Key Characteristics:
- Assigned by: Your Internet Service Provider (ISP)
- Visibility: Visible to external websites and services
- Quantity: Typically one per network (shared by all devices)
- Uniqueness: Must be globally unique to avoid routing conflicts
- Also known as: External IP address
When you browse the internet, stream videos, or send emails, external servers see your public IP address—not your device's private IP. This is the address websites log when you visit them and the one that appears when you check "What is my IP?" on our homepage.
Did You Know?
Most residential internet connections use dynamic public IP addresses that change periodically. This happens when:
- Your router is restarted
- Your ISP performs network maintenance
- You connect to a different network
Business connections often use static public IPs that never change, allowing them to host servers and services reliably.
Check your current public IP address:
Visit whatismyip.bz
Private IP Addresses: Your Local Network Identity
Private IP Ranges
Private IP addresses must fall within specific reserved ranges:
| Class | Range | Common Usage |
|---|---|---|
| Class A | 10.0.0.0 — 10.255.255.255 | Large enterprise networks |
| Class B | 172.16.0.0 — 172.31.255.255 | Medium-sized networks |
| Class C | 192.168.0.0 — 192.168.255.255 | Home networks (most common) |
If your device's IP starts with these numbers, you're looking at a private IP address.
Private IP addresses function exclusively within your local network, allowing your devices to communicate with each other without connecting directly to the internet.
Key Characteristics:
- Assigned by: Your router or network device
- Visibility: Only visible within your local network
- Quantity: Each device on your network has its own private IP
- Uniqueness: Must be unique within your network only
- Also known as: Local IP or internal IP address
Private IPs enable your devices—computers, phones, smart TVs, printers—to identify and communicate with each other within your home or office network.
How Public and Private IPs Work Together
Ever wondered how multiple devices in your home can all access the internet simultaneously with just one public IP address? The magic happens through a process called Network Address Translation (NAT).
The NAT Process:
- Your device (with a private IP like 192.168.1.5) requests a webpage
- Your router records this request in its translation table
- The router replaces your private IP with its public IP and forwards the request to the internet
- When the response arrives, the router checks its translation table
- The router forwards the response to your specific device's private IP
This system allows numerous devices to share a single public IP address while maintaining their unique identities within your local network—solving the problem of IPv4 address scarcity.
Historical Context
In the early days of the internet, each connected device received its own public IP address. As the internet grew exponentially, it became clear that the 4.3 billion possible IPv4 addresses wouldn't be enough.
NAT emerged as an elegant solution to extend the lifespan of IPv4 by allowing entire networks to share a single public address.
While IPv6 was developed to address this limitation with its vast address space, the public/private IP model remains fundamental to how networks operate today.
Finding Your IPs
Public IP:
Simply visit whatismyip.bz to instantly see your public IPv4 and IPv6 addresses, along with location and ISP information.
Private IP:
For macOS:
- Apple menu → System Preferences → Network
- Select WiFi → Advanced → TCP/IP tab
For Windows:
- Start menu → Settings → Network & Internet
- Select Properties from the top menu
Public vs Private IP: Quick Comparison
| Feature | Private IP Address | Public IP Address |
|---|---|---|
| Purpose | Internal device communication | Internet connectivity |
| Network Type | Local Area Network (LAN) | Wide Area Network (WAN) |
| Assignment | By router or DHCP server | By Internet Service Provider |
| Uniqueness Requirement | Only within the same network | Globally unique |
| Visibility | Visible only to local devices | Visible across the internet |
| Address Ranges | Limited to specific reserved ranges | Any valid IP outside private ranges |
| Security | More secure (not directly accessible) | More exposed to potential attacks |
| Cost | Free | Included with internet service |
Frequently Asked Questions
Do I need both a public and private IP address?
Yes, for typical internet usage. Your devices need private IPs to communicate within your network, while your network needs a public IP to connect to the internet. Your router handles the translation between these two systems.
Are local, private, and internal IP addresses the same thing?
Yes, these terms are interchangeable. They all refer to the IP addresses used exclusively within your local network and not visible to the outside internet.
Is a public IP better than a private IP?
Neither is "better"—they serve different purposes. A public IP connects your network to the internet, while private IPs enable communication between devices within your network. Both are essential parts of modern networking architecture.
Can two devices have the same private IP address?
Two devices on different networks can have identical private IPs without issue. However, devices on the same network must have unique private IPs to prevent conflicts and ensure proper routing.
Do I need to hide my private IP address?
No, your private IP address is already hidden from the internet. When you connect to websites or online services, they only see your public IP address, not your device's private IP.
Does a VPN hide my public IP address?
Yes, when you use a VPN (Virtual Private Network), websites and services see the VPN server's public IP address instead of your own. This adds a layer of privacy to your online activities.