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Home/ Blog/ How to check if a proxy server is leaking DNS information?

How to check if a proxy server is leaking DNS information?

PYPROXY PYPROXY · Jun 25, 2025

When using a proxy server to maintain anonymity or improve network security, it's crucial to ensure that the server isn't leaking DNS information. DNS leaks occur when a device sends DNS queries directly to the default DNS servers, bypassing the proxy server and potentially exposing browsing activity to third parties. In this article, we will explore how to detect DNS leaks from a proxy server and offer practical methods to prevent such issues, helping ensure that your online activities remain private and secure.

What is a DNS Leak?

DNS (Domain Name System) is responsible for converting human-readable domain names into IP addresses that computers can understand. When you connect to the internet, your device typically queries a DNS server to resolve domain names. If you're using a proxy server for anonymity, all traffic, including DNS requests, should pass through the proxy. However, if a DNS leak occurs, your device may bypass the proxy for DNS queries, sending them directly to your ISP’s DNS server, thereby exposing the sites you visit.

DNS leaks can compromise your online privacy by revealing your browsing history to third parties, such as your Internet Service Provider (ISP), websites, and hackers. To ensure a proxy server is effectively masking your activity, it’s essential to check for any potential DNS leaks.

How to Check for DNS Leaks?

To determine whether a proxy server is leaking DNS information, you can use several methods, from manual checks to specialized online tools. Below are the most common and effective ways to identify DNS leaks:

1. Use DNS Leak Test Websites

One of the easiest and most popular ways to check for DNS leaks is to use an online DNS leak test tool. These websites can automatically detect DNS leaks by analyzing the IP addresses from which DNS requests are being sent. When using a proxy server, the results should show IP addresses corresponding to the proxy server's DNS servers. If the results display IP addresses of your local DNS server or your ISP, it indicates a DNS leak.

To perform a DNS leak test:

1. Connect to the proxy server.

2. Visit a DNS leak test website.

3. Check the results to ensure that the displayed DNS servers match the proxy server’s DNS addresses.

2. Check the DNS Server Settings Manually

If you're familiar with network configuration, you can manually check the DNS settings on your device to see which DNS servers are being used. The goal is to ensure that the DNS requests are being routed through the proxy server, rather than directly through your ISP’s DNS servers.

For Windows:

1. Open the Command Prompt.

2. Type "ipconfig /all" and press Enter.

3. Check the “DNS Servers” listed under your network connection.

4. Ensure the DNS servers match the ones provided by the proxy service.

For MacOS:

1. Open "System Preferences" and select "Network."

2. Click on your active network connection and then "Advanced."

3. Check the DNS tab to confirm which DNS servers are being used.

If the DNS servers displayed belong to your ISP or a different provider than the proxy, you may be facing a DNS leak.

3. Monitor DNS Requests Using Network Tools

Another way to detect DNS leaks is by using network monitoring tools. Tools such as Wireshark or tcpdump allow you to monitor your device’s network traffic and inspect DNS queries being made. By capturing packets and analyzing DNS requests, you can identify if any DNS queries are being sent outside the proxy server, thereby confirming a leak.

While this method requires some technical knowledge, it offers a more in-depth analysis of network activity and can help detect DNS leaks that are not apparent in basic tests.

4. Use VPN or Proxy Software with Built-in DNS Leak Protection

Some VPN and proxy services come with built-in DNS leak protection features. These tools ensure that DNS queries are routed through their secure DNS servers, preventing any accidental leaks. Many VPN applications automatically perform DNS leak tests to alert users of any potential issues. By using these services, you can ensure that your DNS requests remain protected.

If your VPN or proxy service offers this feature, you can enable DNS leak protection to prevent DNS requests from bypassing the secure server.

5. Testing on Different Networks

Testing for DNS leaks on different networks can be beneficial, especially when traveling or using public Wi-Fi. A DNS leak that appears on your home network might not occur on other networks, and vice versa. By connecting to various networks, you can ensure your proxy server consistently routes all DNS requests through the proxy.

This test helps determine if certain networks or ISPs cause DNS leaks when combined with your proxy server. It's essential to be aware of this, as the location or configuration of the network can impact the success of your DNS leak prevention.

How to Prevent DNS Leaks

If you detect a DNS leak, it's crucial to take immediate steps to prevent it from compromising your online privacy. Here are some solutions to prevent DNS leaks:

1. Use a Reliable Proxy or VPN Service

Choose a high-quality VPN or proxy service that offers DNS leak protection. These services are designed to route all traffic, including DNS queries, through secure servers. Additionally, some VPNs and proxies have features that allow you to manually configure DNS settings, ensuring that all requests go through their secure servers.

2. Change DNS Settings Manually

Another option is to manually configure DNS settings on your device to use DNS servers provided by your proxy or VPN service. This step ensures that all DNS requests are routed through the secure DNS servers of the proxy provider, bypassing any potential leaks to your ISP’s DNS servers.

3. Enable IPv6 Leak Protection

Some proxy and VPN services also provide IPv6 leak protection, which is important as some networks may automatically use IPv6 instead of IPv4, causing potential DNS leaks. Make sure the service you use has IPv6 leak protection enabled.

4. Disable WebRTC and Other Potential Leaks

WebRTC is a technology that can sometimes leak your real IP address and DNS information, even when using a proxy. Disabling WebRTC in your browser settings or using a browser extension designed to block WebRTC can help prevent this type of leak.

DNS leaks can expose your browsing history, undermining the anonymity and privacy that proxy servers are supposed to provide. It's essential to regularly check for DNS leaks and implement preventive measures such as using reliable proxy services, configuring DNS settings, and using VPNs with built-in leak protection. By taking these steps, you can maintain your online privacy and ensure that your DNS queries remain securely routed through the proxy server.

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