Free CGNAT check

Find why inbound connections, hosting, or port forwarding are failing

Check if your internet connection uses CGNAT. The comparison takes the public IP seen by this site and the WAN IP shown on your router status page.

Port Checker NAT Type Check

CGNAT checker

Check your public IP against your router WAN IP

We can see the public IP used for this request. Enter the WAN IPv4 from your router's status page so the checker can compare them.

Your public IP

Checking...

This is the address visible to this site, not the address copied from your router.

Router WAN IPUse the WAN, Internet, Broadband, or External IPv4 shown by the router.

Where do I find my router WAN IP?

Default Gateway / Router address is not the WAN IP

The gateway only helps you reach the router admin page. The checker needs a separate field labelled WAN IP, Internet IPv4, Broadband IPv4, Cellular IPv4, External IPv4, or similar.

Open your router or gateway

Choose the device you are using:

Windows

Run ipconfig in Command Prompt.
Find Default Gateway on the active connection.
Open that gateway address in your browser.
Sign in and find the separately labelled WAN or Internet IPv4.

Using a phone hotspot?

Your phone may not expose the carrier-side WAN IPv4. The Default Gateway on your computer is usually only the local link to the phone. If no WAN IPv4 is available, do not guess.

See the full WAN-IP guide

Router page won't open?

Try HTTPS or check whether the router uses an ISP or manufacturer app. On phone hotspots, workplace Wi-Fi, hotel Wi-Fi, or other managed networks, the upstream WAN address may not be available.

Do not enter your device's own local IP. The checker needs the WAN or Internet IPv4 shown by the router or gateway.

IP comparison

Public IP seen here: Checking...
Router WAN IP: Not entered
Comparison: Waiting for WAN IP

Result

Enter your router WAN IP

The checker needs the WAN or internet IPv4 shown by your router before it can compare anything useful.

Best-effort result. Browser-based checks are best-effort only. They can suggest CGNAT, but they cannot conclusively prove every ISP policy, network topology, or firewall condition.

What to do next

1.Open your router status page and find the WAN, internet, or external IPv4 address.
2.Enter the WAN IP exactly as shown by the router.
3.If the router only shows IPv6, treat this check as informational and confirm connectivity with your ISP or router vendor guidance.

Core tools

Check the network path

Tool

CGNAT Checker

Compare your router WAN IP with your detected public IP and look for strong signs of CGNAT.

Open tool

Tool

Port Checker

Test whether a TCP port appears reachable from the public internet and see the next troubleshooting steps.

Open tool

Tool

NAT Type Check

Understand open, moderate, and strict NAT in plain English and see what to check next.

Open tool

Support guides

Understand the result before changing settings

Guide

Why port forwarding fails

Work through the most common reasons inbound connections stay closed.

Guide

Learn what CGNAT means

Understand why ISPs share IPv4 addresses and how that affects home networking.

Guide

Find your router WAN IP

Locate the internet-facing address shown by your router before you compare it.

Guide

How CGNATCheck works

See the evidence behind the WAN-to-public-IP comparison and the limits of a browser-based check.

Guide

CGNAT vs double NAT

Distinguish provider shared addressing from a second router or gateway in the local path.

Guide

Mobile hotspot, 4G and 5G

Understand what phone tethering can reveal and when a cellular WAN address is unavailable.

Guide

Interpret IPv4 address ranges

Compare public IPv4, RFC1918 private space, and the 100.64.0.0/10 shared range.

Guide

Test port forwarding correctly

Validate the service, protocol, LAN target, firewalls, and external test before judging the result.

More troubleshooting references

ISP guides Router guides CGNAT workarounds Checker methodology

Quick answers

Common CGNAT questions

View all FAQs

What does CGNAT mean?

CGNAT stands for Carrier-Grade Network Address Translation. It lets an ISP place many customers behind shared public IPv4 addresses instead of assigning a unique public IPv4 address to each customer.

Can this checker prove that I am behind CGNAT?

No. This is a best-effort browser check. It can highlight strong signs of CGNAT, but it cannot confirm every network layout or ISP setup from the browser alone.

Why does a private WAN IP matter?

If your router shows a private or shared CGNAT address on its WAN or internet page, that usually means another layer of NAT exists upstream. In many cases that prevents direct inbound connections and port forwarding from working as expected.