// WEBRTC
WebRTC Leak Test
Compare the address your browser advertises over WebRTC with the one this site actually sees.
The test runs entirely in your browser: it opens a throwaway WebRTC connection, collects the addresses your browser is willing to advertise, and compares them with the addresses you already present over ordinary HTTP.
// How WebRTC leaks an IP address
WebRTC is the browser technology behind video calls and peer-to-peer transfers. To connect two people directly it first has to work out what addresses each machine can be reached on, which it does by asking a STUN server 'what address do you see me as?' and by listing local network interfaces. Any web page can start that process without asking permission and read the answers in JavaScript.
That is where the leak comes from. If you are on a VPN, the site you are visiting sees the VPN's address — but if WebRTC is not being routed through the tunnel it may hand out your real address anyway. Your traffic looks protected while your actual address sits in a variable on the page, available to anyone who thought to look.
This test does exactly what such a page would do. It opens a throwaway connection, collects every address your browser is willing to advertise, and compares them with the address our server sees. If they match, WebRTC is not revealing anything extra. If a different public address turns up, that is the leak.
Browsers have narrowed the problem considerably. Chrome and Firefox now replace local network addresses with randomised .local mDNS names, so a page can no longer map your internal network from them. The public-address case is the one that still matters, and it depends on your VPN client rather than on your browser.
If a leak does show up, the fixes in order of preference: switch to a VPN client that handles WebRTC and has a working kill switch; turn on your provider's own leak protection if it offers one; or disable WebRTC in the browser and accept that video calls will stop working — in Firefox that is media.peerconnection.enabled in about:config, and in Chrome it needs an extension.
// Frequently asked questions
- I am not using a VPN and the test shows my real IP. Is that a leak?
- No. Without a VPN or proxy there is nothing for WebRTC to bypass — the address it advertises is the same one every site already sees. This test is only meaningful when you expect your address to be hidden.
- Does this test check for DNS leaks?
- No, and it does not claim to. A genuine DNS leak test needs wildcard DNS infrastructure to observe which resolver your machine queries, which this site does not run. This tests WebRTC only.
- What are the .local addresses it mentions?
- Randomised mDNS hostnames that Chrome and Firefox substitute for your real local IPs before advertising them. They are a privacy feature working as intended, and they rotate regularly.
- Should I just turn WebRTC off?
- Only if you never use browser-based calls. Disabling it breaks video conferencing, screen sharing and some chat apps. For most people a VPN that handles WebRTC correctly is the better answer.
- Does incognito or private mode prevent WebRTC leaks?
- No. Private browsing changes what gets stored on your device, not what your network stack advertises. WebRTC behaves identically in a private window.