What is my NAT type?
Your NAT type describes how your router maps devices on your local network to the public internet. It is not a setting you choose; it is the behavior of the router, the ISP, and the path between them. The type decides whether two peers can open a direct connection or need a relay.
This test runs entirely in your browser. It uses WebRTC and STUN to observe how your public address and port change for different destinations, then classifies the result. There is nothing to install and no account.
NAT types and what they mean
| Result | Behavior | What it means for P2P |
|---|---|---|
| Full Cone (NAT1) | One public mapping for all destinations; any external host can send once the mapping exists. | Easiest to connect. Direct P2P usually works. |
| Address Restricted (NAT2) | Mapping is reusable, but incoming traffic is limited to addresses you have contacted. | Direct P2P usually works after hole punching. |
| Port Restricted (NAT3) | Incoming traffic is limited to the exact address and port you have contacted. | Direct P2P often works, but is less reliable. |
| Symmetric (NAT4) | Each destination gets a different public port mapping. | Direct P2P frequently fails. A relay is the practical fallback. |
| Blocked | Traffic is filtered before it can complete the check. | Firewall, VPN, or network policy is interfering. |
| Unknown | The test could not complete enough probes. | Retry on another network or without a proxy. |
Vendors number NAT types differently. Trust the behavior (cone vs symmetric), not the number.
Why NAT type matters for gaming and remote desktop
Peer-to-peer tools try to connect two devices directly. If both sides are behind symmetric NAT, or one side is behind carrier-grade NAT (CGNAT), the direct path often cannot be established. A TURN relay solves connectivity, but it adds a hop and can cost bandwidth.
The same check is useful before a remote play session: it tells you whether to expect a direct connection or a relay, and whether the problem is your router, your ISP, or the other side. For a deeper guide, see YiLink's network and NAT guide.
How this test works
- Your browser gathers ICE candidates and sends STUN Binding Requests to the probe servers.
- The main server runs two probes from its own public IP. An auxiliary server on a different public IP runs a third probe.
- The server compares the mapped address and port observed by each probe. A different port for a different destination indicates symmetric NAT; a response from the third IP distinguishes Full Cone from Address Restricted.
- The result is returned to your browser. The check usually completes in a few seconds; a timeout means the network filtered the probes.
How to improve a strict NAT type
- Enable UPnP or NAT-PMP on the router if you trust the device and the network.
- Forward the required UDP ports to the machine that needs incoming traffic. For YiLink, see the network guide.
- Try IPv6. If both peers have global IPv6 addresses, NAT is no longer in the path.
- Ask your ISP for a public IPv4 address. If you are behind CGNAT, port forwarding on your router will not help.
- Use a relay when you cannot change the network. A relay is slower than a direct path, but it keeps the session alive.
CGNAT is common on mobile networks, some fiber plans, and shared building networks. A quick sign: your router's WAN address is in a private range (10/8, 172.16/12, 192.168/16) or differs from the public IP shown by this test.
Frequently asked questions
What is my NAT type?
Run the test and read the result. It reports Full Cone, Address Restricted Cone, Port Restricted Cone, Symmetric, Blocked, or Unknown.
Is symmetric NAT bad for gaming?
It is the hardest type for direct P2P. Connections often need a relay or port forwarding, and some games will show a strict NAT warning.
Does this test store my IP address?
The result shows your public IP so you can verify the network path. The test does not require an account. Check the site's privacy policy for retention details.
Why does the test need WebRTC?
WebRTC gathers the ICE candidates and sends the STUN packets used to observe your mappings. A browser without WebRTC cannot run the test.
Why do I get “Unknown” or a timeout?
A VPN, proxy, firewall, or network policy may be filtering UDP. Disable the proxy/VPN and retry, or try another network.
NAT type 3 or 4? You can still connect.
YiLink streams your Windows PC or game to any browser over encrypted P2P, with a relay fallback for strict networks. No client install; the player only needs a link.
Open YiLink