Both "change the IP address" — but at completely different layers and for different purposes. NAT is a routing technique, while a proxy is an intermediary server. Understanding the difference also explains why the router in your home is not a proxy.
The Difference in Layer and Method
NAT changes packet headers and never looks at the content. A proxy, by contrast, terminates the connection and opens a new one on its own behalf.
The Fundamental Difference: Connection Termination
This is the most important distinction between the two techniques:
With NAT the packet stays the same packet; only the address fields change. With a proxy there are two separate connections, and the proxy copies data between them.
NAT in Your Home
Your home router does NAT: it translates the private addresses of the devices inside into a single public IP. This is not a proxy, because:
- You do not have to configure anything on your devices.
- The router does not terminate the connection, it only forwards packets.
- It does not read, filter or cache the content.
- It does not ask for authentication.
We covered CGNAT, its carrier-scale equivalent, in a separate article — and the strength of mobile proxies comes from exactly there.
The Difference in Visibility
Although the result looks similar, the mechanism is different. A proxy can expose the real client by adding headers; NAT cannot, because it never touches the application layer.
Practical Consequences
| Requirement | Is NAT enough? | Is a proxy required? |
|---|---|---|
| Getting multiple devices out through a single IP | Yes | No |
| Going out from a different country | No | Yes |
| Content filtering | No | Yes |
| A different exit per application | No | Yes |
| Access with authentication | No | Yes |
| Keeping access logs | Limited | Yes |
If you say "I want to hide my IP address", NAT already does that — but only within your local network. If you say "I want to go out from another country or with another identity", you need a proxy.
Port Forwarding and Incoming Connections
A well-known limitation of NAT is that it cannot accept incoming connections. Port forwarding is used to get around this. If you are behind CGNAT you cannot use port forwarding, because the public IP is not under your control.
With a proxy the situation is different: a forward proxy is for outgoing connections in the first place; accepting incoming connections is the job of a reverse proxy. We explained the distinction in our forward and reverse proxy article in detail.
Summary
NAT is a routing technique that rewrites packet headers at the network layer; a proxy is an intermediary server that terminates the connection and opens a new one on its own behalf. NAT requires no configuration and is unaware of content; a proxy can handle authentication, filtering, caching and geographic exit selection. The router in your home does NAT, not proxying — which is why you need a proxy when you want to go out from a different country. For the options, see residential and ISP proxy pages.