If you've set up a proxy, configured a VPN, or built a browser automation workflow, you've probably assumed that the IP your browser reports to external sites is the one you chose. WebRTC leaks are the reason that assumption is often wrong — and they're responsible for a surprising number of account flags, fingerprint inconsistencies, and privacy failures that developers trace back to the wrong place.
This guide covers exactly what WebRTC leaks are, why they happen at the protocol level, how to detect them manually and programmatically, and how to fix them in Chrome, Firefox, and Node.js-based automation environments.
What WebRTC Actually Does
WebRTC (Web Real-Time Communication) is a browser API built for peer-to-peer communication — video calls, voice chat, file transfer — without needing a plugin or server relay. To establish a direct connection between two devices, WebRTC needs to know both devices' actual IP addresses. It collects these through a process called ICE (Interactive Connectivity Establishment), which queries STUN servers to discover public IPs and gathers local network interface addresses simultaneously.
The result is a list of ICE candidates: a set of IP addresses and ports the browser is willing to use for a peer connection. This list typically includes your local LAN IP (192.168.x.x or 10.x.x.x), your public ISP-assigned IP, and any IPv6 addresses associated with your network interfaces.
Here's the problem: this IP discovery process happens at the browser level, using the underlying network stack — not through the proxy or VPN tunnel your traffic normally routes through. A proxy changes the IP your HTTP requests appear to come from. It does not prevent the browser from querying STUN servers directly via UDP and reporting back whatever IPs it finds on your actual network interfaces.
That mismatch is a WebRTC leak. Your HTTP traffic shows a proxy IP in Germany. Your WebRTC candidates show your real residential IP in the United States. Any site running standard fingerprinting JavaScript can see both.
Why This Matters for Proxy and Automation Workflows
For general browsing with a VPN, a WebRTC leak is a privacy concern. For anyone doing multi-account management, scraping, or ad verification with proxies, it's a workflow-breaking problem.
Modern anti-bot systems don't just check your HTTP connection IP. They compare it against WebRTC candidates, DNS resolver behavior, browser fingerprint signals, and geolocation data simultaneously. A profile where the HTTP IP says one country and WebRTC candidates say another country has an obvious inconsistency that elevates the risk score immediately — often enough to trigger a checkpoint or block without any other suspicious behavior.
For anti-detect browser users, this is particularly important because most profiles are built around maintaining a coherent identity across all signals. A WebRTC leak punches a hole in that identity at the network layer.
What Types of Leaks Exist
There are four distinct WebRTC leak types worth understanding:
Public IP leak — WebRTC exposes your real ISP-assigned public IP through ICE candidates, even while HTTP traffic routes through a proxy. This is the most damaging leak type because the exposed IP is directly tied to your real identity.
Local IP leak — WebRTC exposes a LAN address (192.168.x.x, 10.x.x.x, 172.16.x.x). Less critical for privacy than a public IP leak, but still contributes to fingerprint uniqueness — the same LAN IP appearing across profiles creates a cross-profile linkage.
IPv6 leak — IPv6 addresses are typically public and globally unique, unlike IPv4 LAN addresses. If your machine has an IPv6 address and WebRTC includes it in ICE candidates while your proxy only tunnels IPv4, the IPv6 address directly identifies your device. This is one of the most overlooked leak vectors in 2026.
mDNS obfuscation disabled — Chromium-based browsers replaced local IP exposure with mDNS hostnames (a random UUID like a3f2c1d0.local) in recent versions to mitigate LAN IP leaks. If mDNS obfuscation is disabled in your browser profile, raw LAN IPs are exposed instead.
How to Test for a WebRTC Leak
Manual browser test
The simplest test is loading a WebRTC leak checker in the browser you want to verify. The NodeMaven WebRTC leak test runs automatically on page load, collects ICE candidates from your browser, and compares them against your HTTP connection IP in a side-by-side display. If WebRTC candidates show any IP other than your proxy IP — especially a public IP from your real ISP — you have a leak.
The test also displays SDP output, which is useful for debugging automation environments where you need to see exactly what candidates the browser is generating.
Run this test every time you:
Configure a new proxy or change proxy providers
Update your browser or anti-detect browser profile
Add or change browser extensions related to privacy or networking
Set up a new automation environment
Manual JavaScript test
To understand what browsers expose at the API level — and to build your own detection logic into a workflow — you can run the ICE candidate collection process directly:
async function detectWebRTCLeak() {
const candidates = [];
const pc = new RTCPeerConnection({
iceServers: [
{ urls: 'stun:stun.l.google.com:19302' },
{ urls: 'stun:stun1.l.google.com:19302' }
]
});
// Create a data channel to trigger ICE gathering
pc.createDataChannel('');
pc.onicecandidate = (event) => {
if (!event.candidate) return;
const candidate = event.candidate.candidate;
// Extract IP addresses from SDP candidate strings
const ipRegex = /([0-9]{1,3}(\.[0-9]{1,3}){3}|[a-f0-9]{1,4}(:[a-f0-9]{1,4}){7})/;
const match = candidate.match(ipRegex);
if (match) {
candidates.push({
ip: match[1],
type: candidate.includes('typ host') ? 'host' :
candidate.includes('typ srflx') ? 'srflx' : 'other',
raw: candidate
});
}
};
await pc.createOffer().then(offer => pc.setLocalDescription(offer));
// Wait for ICE gathering to complete
await new Promise(resolve => {
pc.onicegatheringstatechange = () => {
if (pc.iceGatheringState === 'complete') resolve();
};
setTimeout(resolve, 3000); // Fallback timeout
});
pc.close();
return candidates;
}
detectWebRTCLeak().then(candidates => {
console.log('WebRTC ICE candidates found:');
candidates.forEach(c => console.log(${c.type}: ${c.ip}));
});
The srflx (server-reflexive) candidates are the most important to examine — these are your public IPs as seen by the STUN server. If any srflx candidate shows an IP that doesn't match your proxy's exit IP, you have a public IP leak.
How to Fix WebRTC Leaks
Chrome and Chromium-based browsers
Chrome doesn't have a built-in toggle to disable WebRTC. The recommended approach is the WebRTC Network Limiter extension (official Google extension). In the extension settings, set the policy to "Use my default public interface only". This restricts WebRTC to using the same IP as your HTTP traffic rather than discovering all available interfaces.
For stricter control, the "Disable non-proxied UDP" option prevents WebRTC from making any UDP connections that don't go through the configured proxy. This eliminates leaks entirely but also breaks in-browser WebRTC applications like Google Meet.
For Chromium-based browsers in an automation context, the launch flag approach is cleaner:
chromium --force-webrtc-ip-handling-policy=disable_non_proxied_udp \
--proxy-server=http://user:pass@host:port
The disable_non_proxied_udp policy is the most reliable option for scraping and automation environments where you don't need WebRTC functionality.
Firefox
Firefox is the easier browser to configure for WebRTC leak prevention. Open about:config, search for media.peerconnection.enabled, and set it to false. This disables WebRTC peer connections entirely — no ICE candidates are generated, no IPs are exposed.
If you need WebRTC to remain functional but want to restrict which IPs it exposes, set media.peerconnection.ice.default_address_only to true. This limits ICE candidates to the default network interface rather than enumerating all available interfaces.
// Firefox about:config settings for WebRTC leak prevention:
// media.peerconnection.enabled = false // Disable WebRTC entirely
// media.peerconnection.ice.default_address_only = true // Restrict to default interface
// media.peerconnection.ice.no_host = true // Block local IP candidates
For proxy users who want to keep WebRTC active while preventing leaks, media.peerconnection.ice.default_address_only = true combined with a SOCKS5 proxy configured at the browser level (not system level) is the most reliable configuration.
Puppeteer and Playwright
In Node.js automation with Puppeteer, set the WebRTC policy at browser launch:
const puppeteer = require('puppeteer');
const browser = await puppeteer.launch({
args: [
'--force-webrtc-ip-handling-policy=disable_non_proxied_udp',
'--proxy-server=http://user:pass@host:port',
'--disable-features=WebRtcHideLocalIpsWithMdns' // Only if you want raw IPs (testing)
]
});
const page = await browser.newPage();
// Verify no WebRTC leak programmatically
const candidates = await page.evaluate(async () => {
const found = [];
const pc = new RTCPeerConnection({
iceServers: [{ urls: 'stun:stun.l.google.com:19302' }]
});
pc.createDataChannel('');
await pc.createOffer().then(o => pc.setLocalDescription(o));
await new Promise(r => setTimeout(r, 2000));
pc.onicecandidate = e => { if (e.candidate) found.push(e.candidate.candidate); };
pc.close();
return found;
});
console.log('ICE candidates from automated browser:', candidates);
// Should be empty or show only proxy IP if configured correctly
For Playwright, the equivalent configuration:
const { chromium } = require('playwright');
const browser = await chromium.launch({
args: [
'--force-webrtc-ip-handling-policy=disable_non_proxied_udp'
],
proxy: {
server: 'http://host:port',
username: 'user',
password: 'pass'
}
});
Anti-detect browsers
Anti-detect browsers handle WebRTC at the profile level. In AdsPower and Dolphin Anty, the WebRTC setting in each browser profile controls whether the profile exposes the proxy IP, a spoofed IP, or disables WebRTC entirely. The correct setting for most proxy workflows is to configure WebRTC to return the proxy IP rather than disabling it — a profile with WebRTC completely absent is itself a fingerprint signal, since almost no real browsers have it disabled.
The profile-level WebRTC setting needs to be verified after each proxy change. If you reassign a profile to a different proxy IP but the WebRTC setting still references the old IP, the inconsistency is detectable.
The Proxy and WebRTC Relationship
One important clarification: WebRTC leaks are a browser configuration problem, not a proxy quality problem. A high-quality residential proxy routes your HTTP traffic through a clean IP. It cannot, on its own, prevent the browser from generating ICE candidates using your real network interfaces via UDP.
That said, the quality of the proxy still matters for the overall setup. A clean proxy IP that matches the geographic location and ISP profile you're projecting creates a coherent identity. If your browser is correctly configured to route WebRTC through the proxy (or to disable non-proxied UDP), the ICE candidates will reflect the proxy IP, and the HTTP connection and WebRTC layer will be consistent. For workflows where IP reputation is critical — multi-account management, ad verification, scraping — residential proxies with pre-filtered IPs give you a stable foundation that WebRTC configuration alone can't provide.
For residential proxy workflows specifically, cross-linking the NodeMaven DNS leak test into your pre-flight checklist alongside the WebRTC test is worth doing — DNS leaks are a separate vector that can expose your real resolver even when WebRTC is properly handled.
Verification Checklist Before Any Proxy Workflow
Before running any account management, scraping, or automation session, run through this verification sequence:
Activate your proxy and confirm the HTTP exit IP matches your expected location
Run the WebRTC leak test — verify no ICE candidates show your real public IP
Check for IPv6 leaks specifically — IPv6 is the most commonly overlooked vector
Run a DNS leak test — verify your DNS resolver matches your proxy's location
If using an anti-detect browser, confirm the WebRTC setting in the active profile reflects the current proxy IP
Re-run verification after any browser update, extension change, or proxy rotation
The most common mistake is running verification once during initial setup and never again. Browser updates silently change WebRTC behavior. Extensions conflict after updates. A clean setup from three months ago may have a leak today.
Quick Reference: WebRTC Settings by Environment
WebRTC leaks are one of the most reliable ways a browser-based workflow gets fingerprinted, and they're entirely fixable with the right configuration. The test takes under 30 seconds. The fix is a single browser setting or launch flag. Running both as a standard pre-flight check costs almost nothing and eliminates an entire class of detection failure.
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