DNS Leak vs WebRTC Leak: What Is the Difference?
Both DNS leaks and WebRTC leaks can expose your browsing activity when using a VPN, but they are fundamentally different problems with different solutions. Here is what you need to know about each.
Using a VPN gives you a false sense of security if your connection is leaking data through overlooked pathways. Two of the most common and overlooked leaks are DNS leaks and WebRTC leaks. Both can expose your browsing activity and, in the case of WebRTC, even reveal your real IP address — despite your VPN being connected.
Understanding the difference between these leaks, how they occur, and how to fix them is essential for anyone who relies on a VPN for privacy.
What Is a DNS Leak?
DNS (Domain Name System) is the internet's phone book. When you type a website address into your browser, your device sends a DNS query to translate that human-readable name (like google.com) into a numerical IP address that computers use to communicate.
Normally, these queries are sent to your ISP's DNS servers, which means your ISP can see every website you visit before you even connect to it. A VPN is supposed to intercept these queries and send them through the encrypted VPN tunnel to the VPN provider's DNS servers instead.
A DNS leak occurs when DNS queries bypass the VPN tunnel and go directly to your ISP's servers. This happens due to improper VPN configuration, network settings, or Windows features that prioritize speed over security. When a DNS leak occurs, your ISP can see every website you visit in real time — completely defeating the privacy purpose of your VPN.
How Do DNS Leaks Happen?
Several factors can cause DNS leaks:
- Windows IPv6 tunneling: If your ISP uses IPv6 but your VPN does not handle IPv6 properly, DNS queries can leak through the native connection.
- Smart multi-homed DNS: Windows 10 and 11 have a feature that sends DNS queries to multiple servers simultaneously for speed. This can cause queries to reach your ISP's DNS even when VPN DNS is available.
- VPN software misconfiguration: Some VPN clients do not properly redirect DNS traffic, especially when connecting or reconnecting.
- Network manually configured for certain DNS: If your network adapter has manually configured DNS servers, these may override VPN DNS settings.
How to Test for DNS Leaks
The easiest way to test for DNS leaks is to visit a DNS leak test website while connected to your VPN. These services display the IP addresses of the DNS servers resolving your queries. If you see your ISP's DNS servers instead of your VPN provider's servers, you have a DNS leak.
We have a full guide on how to run a DNS leak test and interpret the results.
How to Fix DNS Leaks
Most reputable VPN providers include built-in DNS leak protection that forces all DNS queries through their servers. Look for this feature in your VPN settings and ensure it is enabled. Additionally:
- Disable IPv6 on your network adapter
- Manually configure your DNS servers to your VPN provider's DNS
- Use the VPN provider's official app rather than third-party VPN clients
- Ensure your Windows network profile is set to "metered" or disable the Smart Multi-Homed DNS feature via registry edits
What Is a WebRTC Leak?
WebRTC (Web Real-Time Communication) is a browser technology standardized by the W3C that enables direct peer-to-peer communication between browsers — used for video calls, live streaming, file sharing, and other real-time features. It is built into all modern browsers including Chrome, Firefox, Safari, and Edge.
WebRTC uses STUN (Session Traversal Utilities for NAT) and TURN (Traversal Using Relays around NAT) protocols to discover the best path between peers. Part of this process involves discovering the local and public IP addresses of both peers — and this is where the privacy problem arises.
A WebRTC leak occurs when your browser reveals your real IP address (including local network IPs and sometimes your true public IP) to websites or other parties through WebRTC's ICE (Interactive Connectivity Establishment) candidate discovery process, even while you are connected to a VPN.
Why WebRTC Leaks Are Dangerous
Unlike DNS leaks, which expose your browsing activity to your ISP, WebRTC leaks can directly expose your real IP address to websites you visit. This is particularly problematic because:
- The leak happens silently in the background without any user interaction
- It can occur even when your VPN is functioning correctly
- Blocking cookies or using incognito mode does not prevent it
- Many users are completely unaware it is happening
A website can use a simple JavaScript snippet to initiate a WebRTC connection and collect your real IP address — all without asking your permission or displaying any visible indication.
How to Test for WebRTC Leaks
You can test for WebRTC leaks by visiting a WebRTC leak test page with your VPN connected. These tests display all IP addresses that your browser reveals through WebRTC. If you see your real public IP address or local network addresses, you have a WebRTC leak.
How to Fix WebRTC Leaks
There are several approaches to preventing WebRTC leaks:
- Browser settings: Firefox allows you to disable WebRTC entirely via about:config (set media.peerconnection.enabled to false). Chrome requires an extension like uBlock Origin or WebRTC Leak Prevent.
- VPN browser extension: Some VPN providers offer browser extensions that include WebRTC leak protection. These are typically more convenient than global browser changes.
- Use a leak-proof browser: Some privacy-focused browsers have WebRTC leaks disabled by default.
- Always verify: Test after every browser update, as these sometimes re-enable WebRTC features.
DNS Leak vs WebRTC Leak: Key Differences
While both are privacy leaks, they are fundamentally different in nature:
| Aspect | DNS Leak | WebRTC Leak |
|---|---|---|
| What it exposes | Browsing activity (websites visited) | Real IP addresses (local and/or public) |
| Who can see it | Your ISP (primarily) | Websites and services you use |
| Technical cause | DNS queries routing to ISP DNS servers | WebRTC ICE candidate discovery in browsers |
| Easiest fix | Enable VPN DNS leak protection + disable IPv6 | Disable WebRTC in browser or use extension |
| Affected platforms | All devices and operating systems | Primarily desktop browsers (less common on mobile) |
Which Is More Dangerous?
In terms of direct privacy harm, a WebRTC leak is generally more dangerous because it directly exposes your IP address — which is the primary identifier a VPN is supposed to hide. Your real IP address can be used to:
- Identify your geographic location with surprising accuracy
- Link your VPN sessions to your real identity over time
- Track you across websites if combined with other data
- Confirm you are using a VPN if multiple connections from the same IP are observed
A DNS leak is primarily a problem because it reveals your browsing activity to your ISP. While this is a significant privacy concern — especially in countries with invasive surveillance — it does not directly expose your identity the way a WebRTC leak can.
However, both should be addressed. A comprehensive VPN privacy setup includes protection against both types of leaks.
VPNs with the Best Leak Protection
When choosing a VPN, look for providers that specifically address both DNS and WebRTC leaks:
NordVPN
NordVPN includes built-in DNS leak protection that is enabled by default, along with CyberSec (their threat protection feature) which blocks malicious domains. They also offer browser extensions with WebRTC leak prevention.
ExpressVPN
ExpressVPN includes automatic DNS leak blocking and their proprietary TrustedServer technology runs all DNS queries through their own servers. Their browser extension also prevents WebRTC leaks. They are among the best for leak protection out of the box.
Mullvad
Mullvad, the privacy-focused Swedish provider, has DNS leak protection built into their VPN client and recommends disabling WebRTC in browsers for maximum privacy. They are very transparent about leak risks and how to address them.
Surfshark
Surfshark includes CleanWeb feature which blocks ads and malware at the DNS level, effectively preventing DNS-based tracking. Their One package includes alert systems that notify you if your data appears in breaches.
FAQ: DNS Leaks vs WebRTC Leaks
Can DNS leaks occur on mobile devices?
Yes. Mobile operating systems handle DNS differently than desktops, and both iOS and Android can experience DNS leaks. The risk is particularly high on Android due to the way the OS handles IPv6. Using your VPN provider's official app (rather than third-party) and enabling DNS leak protection in settings is important on mobile.
Do all VPNs cause WebRTC leaks?
Not all. Quality VPN providers have taken steps to prevent WebRTC leaks in their applications, particularly in browser extensions. However, the leak originates from the browser itself, so even with a VPN connection, an unprotected browser can expose IP addresses through WebRTC. The browser or its extensions must have WebRTC leak protection to fully prevent this.
Can I completely disable WebRTC?
In Firefox, you can completely disable WebRTC via about:config (media.peerconnection.enabled = false). In Chrome, WebRTC cannot be fully disabled without browser flags that may affect functionality, but extensions like uBlock Origin or WebRTC Leak Prevent can block the IP discovery. Note that disabling WebRTC may break some legitimate features like video calling or live streaming.
Do I need to test for leaks every time I use my VPN?
We recommend testing after any significant change: installing browser updates, changing VPN servers, updating your VPN app, or changing network configurations. If your setup is stable and you have leak protection enabled, testing once a month or after updates is sufficient.
What is an IPv6 leak and how does it relate to DNS leaks?
An IPv6 leak occurs when IPv6 traffic bypasses the VPN tunnel and goes directly over your ISP's native connection. This can cause both DNS leaks (IPv6 DNS queries going to your ISP) and privacy leaks (your real IPv6 address being exposed). Disabling IPv6 on your network adapter or using a VPN that properly handles IPv6 is the solution.
Does a kill switch prevent DNS and WebRTC leaks?
A kill switch prevents your real IP address from being exposed when the VPN connection drops by blocking internet traffic entirely. However, it does not prevent DNS leaks that occur while the VPN is actively connected, nor does it prevent WebRTC leaks which happen at the browser level regardless of VPN connection status. You need specific DNS leak protection and WebRTC leak prevention for those issues.
The Bottom Line
DNS leaks and WebRTC leaks are two distinct vulnerabilities that both represent significant privacy risks — but neither is inevitable. Quality VPN providers include built-in protection against both, and browser-level precautions can address the WebRTC issue for browsers where it is most problematic.
The key is to test regularly, understand your VPN's leak protection features, and take browser-level precautions for WebRTC. With the right setup and regular testing, you can achieve the level of privacy that justifies relying on a VPN.
For more on testing your VPN setup, see our complete guide to how to run a DNS leak test. And to find VPNs with the best leak protection, see our comparisons of no-log VPNs and VPNs for privacy.
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