Chrome vs. Firefox: Why Do DNS Leak Test Results Differ?

Many people encounter a confusing issue when performing DNS leak tests or DNS leak detection: under the same network environment, switching browsers produces different results.

Especially with Chrome and Firefox, the detected DNS servers, IP geolocation, and even the number of leaks can vary.

In fact, these differences are completely normal from a technical perspective, and there is a clear logic behind them. Let’s break it down and explain what’s really going on.

1. First, what exactly does a DNS Leak Test measure?

When you visit a website, a DNS leak test checks whether your domain name resolution requests (DNS requests) bypass your VPN or proxy and go directly through your local network or ISP DNS.

Under normal circumstances, if you are connected to a VPN:

•  DNS requests should go through the DNS assigned by the VPN

•  The externally visible DNS IP should match the VPN node’s location

If the test results show:

•  Local ISPs (Telecom / Unicom / Mobile)

•  Your real domestic IP location

•  Or DNS servers completely inconsistent with the VPN country

Then there is basically a DNS leak risk.

2. Why do Chrome and Firefox show different DNS leak test results?

1️⃣ Chrome enables “Secure DNS / DoH” by default

Starting from earlier versions, Chrome has enabled DNS over HTTPS (DoH) by default, also known as “Secure DNS.”

Its characteristics include:

•  DNS requests are encrypted via HTTPS

•  In many cases, it directly uses Google DNS or Cloudflare DNS

•  It may bypass system-level DNS settings

As a result, when running a DNS leak test, Chrome often displays public or encrypted DNS instead of the DNS provided by the VPN.

That’s why you may see:

•  Chrome: appears “not leaking”

•  Firefox: exposes local DNS

This doesn’t mean Firefox is less secure—rather, Chrome bypasses the system DNS testing path.

2️⃣ Firefox offers more “transparent” DNS control

Firefox’s DNS strategy is relatively conservative:

•  By default, it respects the operating system’s DNS

•  DoH usually requires manual configuration or explicit opt-in

•  It reflects VPN and proxy DNS paths more accurately

Therefore, in DNS leak detection scenarios:

•  Firefox is more likely to expose real DNS issues

•  It is also better for troubleshooting VPN or system-level leaks

Many privacy-focused users deliberately use Firefox for testing for this reason.

3. Browser fingerprint detection also affects DNS test results

Many people overlook one point: DNS leak testing websites themselves also combine browser fingerprint detection. For example:

•  Browser type

•  Network stack behavior

•  WebRTC

•  IPv6 support

All of these influence the testing logic.

If you use platforms such as the ToDetect fingerprint lookup tool, you’ll find that:

•  Chrome and Firefox have very different network fingerprints

•  Certain DNS request paths are only triggered in specific browsers

This is why the same DNS leak test site shows different results when you switch browsers.

The core issue is not inaccurate testing, but different browser behaviors.

4. WebRTC and IPv6: hidden “leak accelerators”

WebRTC: Chrome enables WebRTC by default

Even with a VPN enabled, your local IP may still be exposed, and DNS test sites sometimes capture WebRTC information as well.

IPv6: Chrome provides more aggressive IPv6 support

Firefox disables or restricts it by default on some systems.

If the VPN does not properly handle IPv6, test results can become inconsistent.

This is also why many people see Chrome reporting strange DNS entries while Firefox appears relatively “clean.”

5. Practical tips for proper DNS Leak Detection

If you want more reliable conclusions, follow these suggestions:

Test with at least two browsers

•  Chrome + Firefox is the most basic combination

•  Unify settings before testing

•  Keep DoH enabled or disabled consistently

•  Unify WebRTC and IPv6 policies

•  Combine with browser fingerprint detection tools, such as the ToDetect fingerprint lookup tool.

Check whether network fingerprints, DNS, and IP are logically consistent, and don’t just look at “whether there is a leak.”

•  Also verify whether the DNS ownership is reasonable

•  And whether it matches the VPN node’s country

Summary

Truly rigorous DNS leak detection always involves multiple browsers and multiple perspectives. A more reliable approach is to:

•  Cross-test DNS leaks using different browsers

•  Simultaneously use browser fingerprint detection tools (such as the ToDetect fingerprint lookup tool)

If you are involved in privacy protection, cross-border business, or account environment isolation, analyzing DNS leak testing + browser fingerprint detection together is the correct approach.