Free Tool

Does this network block UDP?

Offices, campuses, hotels and some carriers drop UDP. Then WireGuard and IKEv2 fail to connect while TCP-based protocols keep working. Let us check what the network you are on right now allows.

Ready

Press the button; it takes about six seconds.

How to read the result

The browser asks STUN servers (Google, Cloudflare) to reply over UDP. A reply means UDP passes and WireGuard will very likely connect. No reply while local addresses were found means the network drops UDP, and you need a TCP-based protocol.

What to do if UDP is blocked

In your VPN app pick VLESS (it runs over TCP 443 and looks like ordinary HTTPS) or turn on automatic protocol selection. Background in what is VLESS and VPN not working on Wi-Fi.

Limits of the test

It probes the STUN ports (3478 and 19302), not your VPN server's port. A network may allow one UDP port and drop another, so WireGuard on a non-standard port occasionally still works. Nothing is sent to our servers.

UDP blocked?

404 VPN runs VLESS over TCP 443: where UDP is closed, the connection still gets through and looks like an ordinary website.

How to connect 404 VPN →

Frequently asked questions

guest@404vpn:~$ cat udp-block-test-faq.md

[01] $ Why does my VPN work on mobile data but not on Wi-Fi? ▸

> Usually because the office, campus or hotel Wi-Fi blocks UDP. This test shows exactly that. The fix is a TCP protocol such as VLESS.

[02] $ The test says UDP passes but WireGuard still will not connect ▸

> The network may allow STUN ports yet block your server's port, or the problem is not the network: device clock, keys, client version. The checklist is in "VPN not working on Wi-Fi".

[03] $ Does the test send my data anywhere? ▸

> No. The browser only contacts public STUN servers, as it does for any video call; nothing reaches our servers.