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· 6 min read
Best 3 WebRTC Leak Test Tools Compared
Manesh Jayawardhana
CIO & Co-founder
Your VPN says connected, the IP-checking site shows a server in another country, and everything looks fine. Then a web page asks your browser for its WebRTC candidates and gets your real address anyway.
WebRTC is designed for direct browser-to-browser connections — video calls, screen sharing — and to make those work it needs to know what addresses your machine can be reached on. It gathers them at the operating system level, which is underneath the layer most VPNs operate at. That is the leak, and it is a design consequence rather than a bug.
How to judge a leak test
Does it separate local from public? A local 192.168.x.x address leaking is a fingerprinting concern. Your public IP leaking past a VPN is the serious one. Tools that blur them cause needless alarm.
Does it check IPv6? Many VPNs tunnel IPv4 only, leaving an ISP-assigned IPv6 address exposed. It is one of the most common real leaks and the least tested.
Does it compare against a baseline? Knowing WebRTC reports an address is not the finding. Knowing it differs from your VPN’s is.
Who runs it? Most leak testers are operated by VPN review sites or VPN companies. The test can still be accurate; the recommendation that follows it is an advert.
The comparison
| Tool | Best for | Free tier | Watch out |
|---|---|---|---|
| NAT Checker | A three-way comparison against a baseline | Free, no account, no permissions needed | Narrow focus — WebRTC only |
| Privacy Test Lab | Understanding what each result means | Free, no login | Tests several channels at once, more to read |
| vpnMentor IP Leak Test | A broad check including camera and mic | Free, no account | Run by a VPN review site part-owned by VPN providers |
Facts checked August 2026; tools change. Table covers only the 3 alternatives — our tool gets its own section below.
NAT Checker
The most methodologically careful. It gathers host, srflx and relay ICE candidates — the three kinds of address WebRTC collects — and runs a three-way comparison between the IP your normal HTTPS request shows, the addresses WebRTC exposes, and a baseline taken with the VPN disabled. That baseline is what turns a list of addresses into an actual verdict.
It covers IPv4 and IPv6, needs no account, requires no camera or microphone permission, and is free. It does one thing, so a DNS leak or a broader privacy question needs another tool — but for the specific question of whether WebRTC is betraying your VPN, it is the most rigorous of the three.
Privacy Test Lab
The best at explaining itself. It checks four channels at once — your visible HTTP IP, WebRTC, DNS resolver routing and IPv6 — which catches partial leaks that a single-channel test misses entirely. The write-up around the results explains what a WebRTC leak is, what a DNS leak means (queries going to your ISP rather than your VPN’s resolver), and why an IPv6 leak happens when a VPN tunnels only IPv4.
Usefully, it also addresses the confusing case where one channel looks protected and another does not, and suggests specific fixes for each type. No login, free. The trade-off is volume: four results and their explanations is more reading than a single verdict.
vpnMentor IP Leak Test
The broadest single sweep. It separates local IP leaks via WebRTC, public IP leaks via TCP/IP, public IP leaks via WebRTC and IPv6 leaks via WebRTC — a clean breakdown of the distinctions that matter — and additionally checks for exposed camera and microphone devices. It states it does not store or share the information used to run the tests, needs no account, and is free.
The disclosure worth reading is on their own page: vpnMentor is in partnership with Kape Technologies, which owns several VPN providers including ExpressVPN and CyberGhost, and they acknowledge this affects their rankings. The leak test measures what it measures; treat the surrounding recommendations accordingly.
WebRTC Leak Test
Ours tests whether WebRTC exposes your local or public IP addresses to web pages, including while a VPN is connected, running entirely in your browser. It is the focused version — the question and its answer, without a scorecard, an account, or a ranked list of VPNs at the bottom.
What it does not do: check DNS leaks, test IPv6 separately, compare against a VPN-off baseline, or scan for camera and microphone exposure. If you want a full privacy sweep, Privacy Test Lab covers more ground; if you want a rigorous WebRTC verdict, NAT Checker’s baseline comparison is more thorough. MDN’s WebRTC API documentation explains why the browser gathers these addresses in the first place.
Which one to pick
- Confirming a suspected leak rigorously — NAT Checker’s baseline comparison.
- Understanding what the results mean — Privacy Test Lab.
- One sweep across several leak types — vpnMentor, discounting the recommendations.
- A quick check with nothing attached — the tool below.
How to do it with WebRTC Leak Test
- Connect your VPN, then open the WebRTC Leak Test.
- Compare the addresses WebRTC reports against the IP your VPN is meant to be presenting.
- A local address appearing is a fingerprinting concern; your real public IP appearing is a genuine leak.
- If it leaks, disable WebRTC in your browser or use an extension that blocks it, then retest.
The background is in is WebRTC leaking your real IP behind a VPN. Other privacy tools are in the tools directory.
You might also need
WebRTC is one route; DNS is the other. The DNS Leak Tester checks whether your lookups are still going to your ISP.
The Browser Risk Inspector covers what else your browser reveals, which is usually more than people expect.
Frequently asked questions
Is there a free WebRTC leak test that isn’t run by a VPN company?
Ours contacts no external service, and NAT Checker and Privacy Test Lab are not VPN vendors. vpnMentor discloses its partnership with a company that owns several VPN providers — worth knowing when reading its recommendations.
Does a WebRTC leak mean my VPN is broken?
Not necessarily. WebRTC gathers addresses at a level beneath where most VPNs operate, so the leak can happen with a perfectly functioning VPN. Some VPN clients and browser extensions block it specifically; many do not.
How do I stop WebRTC leaking?
Disable WebRTC in the browser if you never make calls in it, use an extension that blocks the address-gathering, or use a VPN client that handles it. Then retest — the fix is easy to apply and easy to get wrong.
Final thought
Test with the VPN on and off, and compare. A single reading in isolation tells you what addresses exist; only the comparison tells you whether anything is actually escaping.