Firefox privacy settings everyone's using: How to easily stop DNS leaks

Nowadays, people engaged in cross-border e-commerce and social media operations commonly use the Firefox browser. If it is not properly configured, DNS leaks can easily occur.

This may not only expose your real IP address, but also allow your browsing activity to be monitored, leading to account association—resulting in restrictions or even account bans in severe cases.

In this guide, we will walk you step by step through a practical tutorial on fixing DNS leaks in Firefox, including DNS leak testing methods and browser configuration tips.

1. What is a DNS leak? Why should you care?

DNS (Domain Name System) works like the internet’s phonebook, converting the website you enter into its corresponding IP address. When using a VPN or proxy, if your browser still uses the default DNS, it can result in a DNS leak.

Common risks caused by DNS leaks include:

•  Exposure of your IP address and tracking of your location

•  Monitoring or analysis of your browsing activity

•  Failure to access restricted content using IP-based tools

Therefore, properly configuring Firefox is crucial to preventing DNS leaks.

2. How to test if your DNS is leaking?

Before fixing the issue, you should first check whether your browser actually has a DNS leak. A simple method is:

•  Open the Firefox browser

•  Visit DNS leak testing websites such as dnsleaktest.com or other accessible tools

•  Check whether the displayed DNS servers match your VPN or proxy

If the DNS servers shown belong to your local ISP, it means your Firefox browser has a DNS leak and needs to be configured.

3. Comparison of popular DNS providers

💡 Tip: If your main goal is to prevent DNS leaks, prioritize DNS providers that support DoH and combine them with custom DNS settings in Firefox for maximum privacy protection.

4. Step-by-step guide to fixing DNS leaks in Firefox

Below is a complete workflow based on practical experience to help you maximize DNS security in Firefox.

1. Enable DNS over HTTPS (DoH)

Firefox provides DNS over HTTPS, which sends DNS requests through an encrypted channel to prevent ISP monitoring. Steps:

•  Open Firefox and enter about:preferences#general in the address bar

•  Scroll to Network Settings → Settings

•  Check Enable DNS over HTTPS

•  Choose a reliable provider (e.g., Cloudflare or NextDNS)

•  Save and restart the browser

This resolves most DNS leak issues at the browser level.

2. Disable WebRTC to prevent IP leaks

WebRTC enables real-time communication but may bypass VPNs and expose your real IP. Steps:

•  Enter about:config in the address bar

•  Search for media.peerconnection.enabled

•  Set it to false

3. Configure custom DNS in Firefox

If you want full control over DNS, you can configure it manually:

1. Go to about:preferences#general → Network Settings → Settings

2. Select Use custom DNS and enter trusted DNS addresses, such as:

•  Cloudflare: 1.1.1.1 / 1.0.0.1

•  Google: 8.8.8.8 / 8.8.4.4

3. Save the settings: even if your VPN fails, it won’t fall back to ISP DNS.

4. Clear browser cache and cookies

DNS leaks may sometimes be affected by cache, so it’s recommended to clean regularly:

•  Firefox Settings → Privacy & Security → Cookies and Site Data → Clear Data

•  Use private browsing mode and fingerprint detection tools to verify results

5. Use ToDetect fingerprint detection tool

1. Visit the ToDetect fingerprint checking website

2. Check whether your IP, DNS, screen resolution, plugins, and other data are exposed

3. Adjust Firefox settings based on the results

Through repeated testing and adjustments, you can ensure both DNS leak tests and browser fingerprint checks show secure results, maximizing your privacy protection.

Summary

Although DNS leaks may sound technical, proper Firefox configuration can effectively prevent privacy exposure.

Combined with the ToDetect fingerprint detection tool, you can thoroughly fix DNS leak issues while also reducing the risk of browser fingerprint tracking.

Make it a habit to regularly test your DNS and browser fingerprint to ensure a secure, private, and efficient browsing experience in Firefox.