WebRTC leaks: how anti-detect browsers fail and how to verify yours
WebRTC leaks: how anti-detect browsers fail and how to verify yours
You set up a proxy, fired up your anti-detect browser, and assumed you were covered. then a platform flagged your account anyway. if you have been in that situation, there is a good chance WebRTC was the culprit. it is one of the most common ways a browser profile bleeds your real identity, and most users only discover it after something has already gone wrong.
i’ve watched people spend money on Multilogin or AdsPower, configure residential proxies correctly, and still get flagged because nobody told them about WebRTC. this explainer covers what the leak is, exactly how it happens at the protocol level, and how to confirm whether your setup is actually clean.
what it is
WebRTC, short for Web Real-Time Communication, is an open standard and browser API that lets web applications establish peer-to-peer connections for audio, video, and arbitrary data, directly in the browser, without plugins. it is what powers Google Meet, Discord’s in-browser calls, and live collaboration tools. the official W3C specification defines the full API surface that browsers implement.
a WebRTC leak happens when a website uses JavaScript to invoke the WebRTC API and, in the process of setting up a potential peer connection, your browser reveals IP addresses that should have stayed hidden. specifically, it can expose your real public IP and your local network IP (the 192.168.x.x or 10.x.x.x address assigned by your router) even if all your HTTP traffic is routed through a proxy or VPN.
that last part is the key failure mode. your proxy handles your web requests. WebRTC operates at a lower level and, unless explicitly blocked or handled by your anti-detect browser, bypasses the proxy entirely.
how it works
to understand why the leak happens, you need to understand what WebRTC does when it tries to connect two peers.
when a browser initiates a WebRTC session, it uses a protocol called ICE, Interactive Connectivity Establishment, to figure out the best network path between two endpoints. ICE is defined in RFC 8445 by the IETF. as part of the ICE process, the browser collects what are called “ICE candidates”: possible network addresses and ports through which a connection could be made.
to gather these candidates, the browser makes requests to STUN servers (Session Traversal Utilities for NAT). STUN servers are designed to tell the browser its public IP address as seen from the outside internet, which is necessary for NAT traversal in legitimate video call scenarios. browsers typically use Google’s public STUN servers (stun.l.google.com:19302 and similar) unless configured otherwise.
here is where the problem occurs. the browser makes these STUN requests through the system’s network stack, not through the browser’s proxy settings. so if you have a proxy configured at the browser level, or even at the OS level in some cases, the STUN requests still go out through your actual ISP connection. the STUN server responds with your real public IP. that IP is included in the ICE candidate list, which is accessible to any JavaScript running on the page.
a site operator with any interest in fingerprinting does not need to actually complete a WebRTC call. they just need to trigger the ICE gathering process and read the candidates. the MDN documentation on the WebRTC API explains the full API that makes this possible. two calls in particular, RTCPeerConnection and createDataChannel, are all that is needed to start candidate gathering.
your local IP (the 192.168.x.x address) is also leaked in this process, even behind a VPN. that local address is fingerprinting data in its own right: it can reveal whether you are on a home network, a data center machine, or a shared hosting environment.
why it matters
account bans on platforms that check for multi-account use. most large platforms, advertising networks, and marketplaces run fraud detection systems that log WebRTC-derived IPs alongside HTTP request IPs. if your proxy shows an IP in Frankfurt but your WebRTC candidates expose your real Singapore ISP address, the two data points conflict. that conflict is a reliable signal for automated fraud detection. if you are running multi-account operations, this is a real operational risk. the folks over at multiaccountops.com cover this exact scenario in depth.
airdrop and DeFi farming. on-chain actions may be pseudonymous, but the browser session before and after a transaction is not. platforms with KYC or Sybil-resistance checks use WebRTC as one signal among many. a consistent real IP appearing across “separate” wallet sessions undermines the separation you are trying to maintain.
advertising arbitrage and affiliate operations. ad networks and affiliate platforms compare the IP they see in your HTTP headers against any WebRTC candidates. mismatches are flagged. this is not theoretical: it is a documented reason for account closures on platforms like Google Ads and major affiliate networks.
fingerprint consistency. even if a specific platform does not act on a WebRTC leak today, the data is logged. if your fingerprint is ever reviewed retroactively, inconsistency between your proxy IP and WebRTC IP is easy to find. browser fingerprinting as a concept covers why logged inconsistencies compound over time.
common misconceptions
“my proxy covers this.” no, it does not, not automatically. a proxy configured at the browser level, or even at the OS network level, routes your HTTP/HTTPS traffic. the WebRTC STUN requests are UDP packets that typically bypass proxy configurations unless the proxy is set up specifically to intercept UDP traffic or unless the anti-detect browser explicitly handles WebRTC. most SOCKS5 proxies do not handle UDP unless configured for it. most anti-detect browsers require you to explicitly disable or spoof WebRTC in the profile settings.
“my VPN handles it.” sometimes, but not reliably. a VPN that routes all traffic including UDP through the tunnel will prevent the STUN leak, but if the VPN has a split-tunnel configuration or if the browser’s WebRTC is not bound to the VPN interface, the real IP still leaks. the only way to know is to test, not to assume.
“anti-detect browsers automatically fix this.” this is where a lot of users get burned. tools like Multilogin, AdsPower, and GoLogin all have WebRTC settings, but they are not always enabled by default in every profile, and they are not all implemented identically. some browsers let WebRTC expose a “real” IP that matches the proxy (spoofing rather than blocking). others disable WebRTC entirely. disabling is cleaner for fingerprint consistency but breaks sites that legitimately need WebRTC for video calls. if you care about which approach your tool uses, read the profile settings documentation for your specific browser version. do not assume.
“only the public IP matters.” the local IP matters too. if your local IP is 192.168.1.x, that is consistent with a home router. if it is 172.17.x.x, that is a Docker bridge network, which suggests an automation or server environment. platforms can use the pattern of local IPs as a signal separate from your public IP.
where to go from here
test your current setup. before changing anything, run a WebRTC leak test. BrowserLeaks is the most commonly cited tool for this. open your anti-detect browser profile with your proxy active and check what IPs appear. if you see anything other than your proxy IP (or nothing at all if WebRTC is fully disabled), you have a leak.
understand the proxy anonymity tiers. WebRTC leaks are one dimension of proxy quality. how to test proxy anonymity walks through the full matrix including HTTP headers, DNS leaks, and WebRTC, so you can evaluate whether a proxy is actually doing what you paid for.
read the anti-detect browser comparison. not every tool handles WebRTC the same way. the best anti-detect browsers comparison covers how each major tool approaches WebRTC spoofing versus blocking, with notes on which versions introduced the feature.
go deeper on fingerprinting mechanics. WebRTC is one leak vector among many. canvas fingerprinting, timezone mismatches, font enumeration, and hardware concurrency all contribute to a fingerprint profile. the full fingerprinting explainer on this blog links to each of these in sequence. if you are running a multi-profile operation seriously, reading through those is not optional.
Written by Xavier Fok
disclosure: this article may contain affiliate links. if you buy through them we may earn a commission at no extra cost to you. verdicts are independent of payouts. last reviewed by Xavier Fok on 2026-05-19.