Before testing for DNS leaks, 99% of people overlook these small details!

Many people’s first reaction when they hear “DNS leak” is to quickly run a DNS leak test. But to put it simply, doing a DNS leak test is like getting a medical checkup — if the environment isn’t properly prepared, the results you get may be completely inaccurate.

Experienced users usually have a habit: before running any formal test, they first check and eliminate potential “interference factors” such as the browser, system settings, and extensions.

Next, we’ll share a few things you should do before running a DNS leak test so that your results will be more accurate.

1. First Confirm Whether Your Browser Environment Is Clean

Before performing any DNS leak detection, the first step is not opening a testing website, but checking your browser environment.

If your browser environment itself exposes real information, your real location might still be identified even if there is no DNS leak.

Many experienced users first use the ToDetect fingerprint checking tool to review their browser fingerprint status before running a DNS test. It can quickly display:

•  IP information

•  Browser fingerprint

•  WebRTC leak status

•  Timezone and language

•  Device information

If this information clearly doesn’t match your network environment, it means your browser environment hasn’t properly isolated your privacy yet.

2. Disable or Restrict WebRTC

WebRTC is a real-time communication technology used by browsers for video calls and peer-to-peer connections. However, it has a side effect — it may directly expose your local IP address.

This can lead to situations where DNS tests appear normal but your real IP is still accessible through WebRTC. Therefore, before running a DNS leak test, check the following:

•  Whether WebRTC is enabled in the browser

•  Whether you are using a WebRTC leak protection extension

•  Whether WebRTC restrictions are configured in browser settings

•  Browsers like Chrome, Edge, and Firefox can limit WebRTC through extensions or about:config.

•  If WebRTC is not handled properly, many people mistakenly believe they have a DNS leak when in fact the browser is simply exposing the local IP.

3. Clear Browser Cache and History

This is something many people overlook. Your browser cache may contain DNS cache records, cookies, local storage data, and site permissions.

These data can affect DNS leak test results. For example:

•  You previously visited some websites and their DNS records are still cached.

•  When you run a DNS leak test, the tool may read old DNS resolution records, causing “mixed DNS servers” to appear.

•  A safer approach is to clear browser cache, delete cookies, and restart the browser.

•  Many professional users even use Incognito / Private Mode when running DNS tests to get cleaner results.

4. Check System DNS Settings

Some DNS leak problems are not caused by the browser but by the operating system itself.

Before performing a DNS leak test, it’s recommended to check the DNS settings of your computer or device, such as:

•  Windows: Control Panel → Network and Sharing Center → Change Adapter Settings → View DNS servers

•  Mac: System Settings → Network → DNS

You should confirm whether a fixed DNS server is configured and whether you are using a public DNS such as Google DNS or Cloudflare DNS.

If your system DNS is manually set, the same DNS server may always appear in test results. This does not necessarily mean a leak — it may simply be your system configuration. Many users misjudge the results at this step.

5. Avoid Browser Extension Interference

Browser extensions are actually a major “variable” in DNS testing. Some common extensions can affect DNS resolution, such as:

•  Ad blocker extensions

•  Privacy protection extensions

•  Security extensions

•  Proxy or network extensions

These extensions may intercept DNS requests, modify resolution paths, or redirect requests, which can lead to abnormal DNS leak test results.

To obtain more accurate results, it is recommended to:

•  Temporarily disable all extensions

•  Or use a clean browser profile

Experienced users often use a dedicated testing browser environment when running DNS leak tests.

6. Use Multiple Tools for DNS Leak Detection

One final tip: don’t rely on just one testing website. Different tools detect different things, such as:

•  DNS servers

•  WebRTC

•  IP routing paths

•  Browser fingerprints

Many experienced users run DNS testing websites + IP checking tools + the ToDetect fingerprint checker together to cross-verify results for better accuracy.

If all three tools show consistent results, you can basically determine whether your network environment has a DNS leak problem.

Summary

Running a DNS leak test is not as simple as opening a testing website. Many misjudgments happen because the environment hasn’t been properly prepared — such as exposed browser fingerprints, WebRTC leaks, incorrect system DNS settings, or extension interference.

Experienced users usually check their browser fingerprint environment first and use the ToDetect fingerprint checking tool to review fingerprint data, while also clearing browser cache and cookies.

DNS testing is only the surface. Preparing the environment is the real key. Once these steps are properly completed, the results you see will be more reliable and you’ll truly know whether your privacy is being leaked.