What is a DNS leak and how to prevent it

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The Domain Name System (DNS) is a critical internet component. It translates human-friendly domain names into IP addresses that computers can understand. However, DNS can also be a weak link in the chain of online privacy.

This post discusses what a DNS leak is, why it's dangerous, and how to prevent it with tools like the best VPN services. Read on to learn about all the steps involved in securing your online privacy.

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What is a DNS leak, and how does it occur? 

A DNS leak occurs when your DNS requests are inadvertently sent to a third-party DNS server instead of the one provided by your virtual private network (VPN) or internet service provider (ISP). This can happen due to misconfigurations, software flaws, or security vulnerabilities. 

DNS leaks ultimately expose your browsing history and online activities to unwanted parties. Common causes of DNS leaks include:

  • Incorrect VPN setup: If your VPN is not configured correctly or lacks proper DNS leak protection, your DNS requests might not be routed through the VPN tunnel.
  • Operating system issues: Some operating systems, like Windows, may prioritize other DNS servers over the ones provided by your VPN or ISP.
  • Network switching: When switching between different Wi-Fi networks or moving between mobile data and Wi-Fi, your device might briefly lose its VPN connection, causing a temporary DNS leak.

Why are DNS leaks dangerous? 

DNS leaks can be detrimental to your online privacy and security for several reasons, such as:

  • Exposed browsing history: Unencrypted DNS requests can reveal the websites you visit and your physical location. This, consequently, undermines the privacy and anonymity provided by VPNs. From marketers to hackers, anyone can use them to profile your online habits.
  • ISP tracking: Your ISP may be able to monitor and log your browsing activities if your DNS requests are leaked. This data can reach third parties, including government agencies. Besides, they may serve the purpose of targeted advertising.
  • Vulnerability to cyberattacks: Hackers can exploit DNS leaks to intercept, redirect, or manipulate your DNS request. This potentially leads to phishing attacks or malware infections. Consequently, your personal or financial information may be exposed to unscrupulous entities.

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How to test for DNS Leaks 

Several online tools are available for testing DNS leaks. These tools display your DNS server's IP address and reveal any leaks by comparing it with your VPN or ISP's DNS server. To test for DNS leaks, you can consider the following steps - 

  • Connect to your VPN: Ensure that you’ve connected your VPN and it's functioning correctly.
  • Visit a DNS leak testing website: Navigate to a reputable DNS leak testing site using your web browser. ExpressVPN provides a good free DNS leak checker, alongside some other useful tools.
  • Run the test: Follow the site's instructions to initiate the DNS leak test.
  • Analyze the results: Check the displayed DNS server IP addresses for discrepancies with your VPN or ISP's DNS servers. If a leak is detected, take appropriate measures to fix it.
  • Run tests regularly: It's essential to check for DNS leaks periodically to ensure your online privacy remains intact.

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How to prevent DNS leaks 

  • Use a VPN with DNS leak protection: Some VPNs offer built-in DNS leak protection to route your DNS requests through encrypted DNS servers. They ensure privacy and security. Thus, research and choose a reputable VPN provider with a proven track record of protecting against DNS leaks.
  • Configure your router's DNS settings: Setting your router's DNS servers to use a trusted and secure provider can help prevent DNS leaks. To do this, access your router's configuration page and update the DNS server settings with the addresses of a secure DNS provider.
  • Use a secure DNS resolver: Services like Cloudflare or Google's can provide a more secure and private DNS resolution, reducing the risk of leaks. These resolvers offer better security features, including DNS-over-HTTPS (DoH) or DNS-over-TLS (DoT). They encrypt your DNS requests and help prevent eavesdropping and manipulation.
  • Disable WebRTC in your browser: WebRTC is a browser feature that can cause DNS leaks. Disabling it or using a browser extension that blocks WebRTC can help prevent leaks. To disable WebRTC, follow the instructions specific to your browser or use a reliable browser extension.
  • Keep your software up-to-date: Regularly update your operating system, VPN client, and browser. This will ensure you have the latest security patches and features and that you can address any known vulnerabilities that could cause DNS leaks.
  • Use a VPN kill switch: A VPN kill switch blocks all internet traffic if the VPN connection drops, helping prevent accidental exposure of your browsing activities. Many VPN providers provide a kill switch feature, so don’t forget to enable it in your VPN settings.
  • Enable DNSSEC: DNSSEC is a security protocol that adds a layer of protection to the DNS by validating the authenticity of the DNS responses. Enabling DNSSEC on your domain can help prevent DNS spoofing and other attacks.
  • Use multi-factor authentication (MFA): To increase the security of your online accounts, consider enabling multi-factor authentication. MFA requires additional verification methods. They may include a one-time code or a biometric identifier, making it more difficult for attackers to gain unauthorized access to your accounts.
  • Use Public Wi-Fi Carefully: Public Wi-Fi networks can be risky, as hackers can easily target them. If you use a public Wi-Fi network, always connect through a VPN to protect your data and maintain your privacy.


A DNS leak can compromise your online privacy and security, making understanding and preventing it essential. Using a reliable VPN with DNS leak protection, configuring your router's DNS settings, and employing secure DNS resolvers can minimize the risk of a DNS leak and maintain your online anonymity. 

Regularly testing for DNS leaks and following other best practices can further strengthen your privacy and security on the internet. By taking these precautions and staying vigilant, you can better protect your online activities and personal information from potential threats.

  • Use a reputable service from a well-known provider. This will minimize the risk of data theft or malware. 
  • Be careful when sharing personal information. Consider avoiding conducting sensitive online activities like banking or shopping using a free VPN.
  • Carefully check your VPN connection to ensure secure and private sessions. Regular checks can help you detect issues and take immediate action. 
  • Implement necessary security measures like installing antivirus and firewalls. This will ensure a comprehensive security solution. 

If you encounter slow speeds or limited bandwidth, try connecting to different servers or using your VPN during off-peak hours. This can help improve performance and reduce the impact of server congestion.

Be aware of the limitations of a free services, and consider upgrading to a paid provider if you require more features, faster speeds, or better security. Many paid VPNs offer affordable plans and additional benefits, such as dedicated streaming servers and advanced security features.

Bottom line

Free services can help you secure your data. However, they usually feature some obvious limitations. For instance, you may need to compromise with the quality of security protocols, agility, and customer support. 

Therefore, consider switching to a paid VPN provider if you use VPNs frequently. With a little research, you may find several budget-friendly alternatives that can help you obtain the best benefits of using a VPN.

Krishi Chowdhary

Krishi is a VPN writer covering buying guides, how-to's, and other cybersecurity content here at Tom's Guide. His expertise lies in reviewing products and software, from VPNs, online browsers, and antivirus solutions to smartphones and laptops. As a tech fanatic, Krishi also loves writing about the latest happenings in the world of cybersecurity, AI, and software.