NAT type check

Find out whether your network is cone or symmetric NAT
NETWORK CHECK

Can the current network reach the peer directly?

检测会向多台公共 STUN 服务器各发一次探测，比较它们看到的外部端口是否一致。 耗时约 3–15 秒，不需要登录，也不会把结果上传到本站。

How to read the result

Public direct The external address matches the local address, or the local address is already public. There is no extra obstacle to a direct P2P connection.
Cone NAT The same local port reuses one public mapping for every target (Endpoint-Independent Mapping). Most home broadband falls into this class, and P2P hole punching succeeds often.
Multi-egress Different targets may see different public IPs (dual WAN, split-tunnel proxies, phone dual-SIM aggregation, carrier IP pools), but ports stay stable within each egress. Detection groups by egress before comparing ports, so this case is never misjudged as symmetric NAT.
Symmetric NAT Each target is assigned a different public port (Endpoint-Dependent Mapping). The peer cannot predict the port, so P2P hole punching rarely succeeds and usually falls back to a TURN relay. Phone hotspots and some corporate or campus networks are common cases.
Multi-layer NAT STUN 看到的外部地址仍落在私有或共享地址段，说明前面还有一层 NAT（例如路由器后面又接了光猫路由）。判断只看 STUN 反射回来的地址，不依赖本机地址是否被浏览器隐藏。

What a browser can measure

The browser does not give web pages a raw UDP socket, so it can only read the srflx candidate addresses. So what is measured here is Mapping behavior: whether the same local port keeps the same external port from every target's point of view.

The comparison first groups by Egress public IP group，只在同一出口内部看端口是否变化。因为双 WAN、分流代理、运营商地址池 本来就会让不同目标看到不同 IP，跨出口的差异不能算作对称 NAT。为了能在单个出口内部比对，服务器清单里 特意保留了两组different ports on the same machine (Xiaomi 3478/3479, Nextcloud 443/3478) — they necessarily go through the same egress.

Full cone / address-restricted / port-restricted whose finer classification belongs to Filtering behavior，需要由另一台服务器主动向你的映射端口发包来验证。 浏览器收不到这种未经请求的 UDP，所以纯前端方案做不到——这不是检测失败，而是浏览器安全模型的边界。 要做完整的 RFC 5780 五分类，需要自建双节点 STUN 服务（两个不同公网 IP 的节点）。

Chrome / Edge hide the local LAN address behind mDNS (xxxx.local）隐藏，所以「本机地址」一栏显示“已隐藏”是正常现象， 不影响映射行为和多层 NAT 的判断。想看到真实内网地址，只能给本站一次摄像头/麦克风权限再重测。

No result detected?

  • No STUN response at all: The current network may be blocking UDP or disabling WebRTC. Corporate networks, some campus networks, and strict proxies or firewalls all cause this. Switch to a phone hotspot to confirm quickly.
  • Only one or two responded: The confidence rating is marked as "low". Some public STUN servers being unreachable across borders is normal; a few more attempts usually gather enough samples to compare.
  • Result differs from the game: The game client uses native UDP against its own servers, so the NAT type only explains "why it will not connect / voice does not work"; it does not replace the in-game network diagnostics.

Privacy: STUN servers will see your public IP — this cannot be avoided. This site neither receives nor stores any detection data.