Detecting and Avoiding Proxy Leaks: WebRTC & DNS

You can configure a perfect proxy and still expose your real IP address through a leak. A proxy leak is any path by which your true IP or location escapes despite the proxy — and because leaks are silent, you often do not know it is happening until an account is linked or blocked. The most common culprits are WebRTC, DNS, and IPv6, each of which can bypass a proxy that only handles ordinary HTTP traffic. Knowing how they leak, and how to check for it, is essential for anyone who relies on a proxy for separation or privacy.

This guide walks through each leak type and how to detect and close it.

WebRTC leaks

WebRTC is a browser technology for real-time audio and video that, by design, tries to discover your device's real IP addresses to establish direct peer connections. It can reveal both your local and public IP through JavaScript, entirely independent of the proxy your browser is configured to use. This means a site can be served your proxy IP for the page request while a WebRTC query quietly hands over your real one — a devastating leak for multi-accounting or privacy.

The fix is to disable or control WebRTC. Anti-detect browsers let you spoof or block WebRTC so it reports the proxy IP or nothing at all; in a normal browser you can disable WebRTC via settings or an extension. Never assume a proxy alone protects you from it.

DNS leaks

Before your browser can reach a site, it looks up the domain via DNS. If those DNS queries go to your own ISP's resolver instead of through the proxy, the ISP — and anyone observing — sees which sites you are visiting, and the resolver's location can betray your real region even though your traffic exits through the proxy. This is a DNS leak.

To prevent it, ensure DNS resolution happens through the proxy or a resolver consistent with your proxy's location, not your local ISP. SOCKS5 configured for remote DNS, proxy software that tunnels DNS, or an anti-detect browser that routes lookups through the proxy all close this gap. Test that your resolver's location matches your exit IP.

IPv6 leaks

Many proxies handle IPv4 only. If your connection and the target both support IPv6, traffic can quietly route over IPv6 and bypass the IPv4 proxy entirely, exposing your real IPv6 address. This is an increasingly common leak as IPv6 adoption grows.

The remedies are to disable IPv6 on the system or browser when using an IPv4-only proxy, or to use a proxy that explicitly handles IPv6. Either way, confirm that no IPv6 address is being exposed alongside your proxied IPv4 one.

Other leak paths

• Timezone and language mismatches: not an IP leak, but a location leak — a browser timezone that contradicts the proxy country flags you.
• Geolocation API: a browser location permission can reveal your real position independent of the IP.
• Proxy failure fallback: if the proxy drops and traffic falls back to a direct connection, you leak until you notice. Use a kill switch or fail-closed setup.
• Application bypass: some apps or system services ignore proxy settings; route them explicitly or block them.

How to test for leaks

Testing is straightforward and should be routine. With your proxy active, use an IP-checking tool — including our What Is My IP tool at /tools/what-is-my-ip — and a dedicated leak test that probes WebRTC, DNS, and IPv6. The result should show only your proxy's IP and location, with no trace of your real address on any channel. If your true IP or ISP appears anywhere, you have a leak to close before doing anything sensitive.

Run this check every time you set up a new profile or environment, not just once. Configurations drift, browsers update, and a setup that was tight last month can start leaking after a change.

The takeaway

A proxy only protects you if every path out of your machine respects it. WebRTC, DNS, and IPv6 are the classic ways your real IP escapes around a proxy, and each has a specific fix: control WebRTC, tunnel DNS through the proxy, and handle or disable IPv6. Add a fail-closed setup so a dropped proxy never silently reverts to a direct connection. Then verify with a leak test — because the whole point of a proxy is that your real IP never shows, and a single leak undoes all of it.