Troubleshooting Slow DNS over HTTPS (DoH): Identifying and Fixing Performance Issues

DNS over HTTPS (DoH) promises enhanced privacy and security by encrypting DNS queries. However, users sometimes experience slower internet speeds when using DoH. This article explores the common causes of slow DoH performance and provides practical troubleshooting steps to improve your connection speed.

Common Causes of Slow DoH Performance

• Overload on the DoH Server: The DNS server you're using might be experiencing high traffic or outages. This is particularly true for popular free DoH providers. Switching to a different server can often resolve this.
• Network Congestion: General network congestion on your internet connection can impact DoH performance as much as it impacts other network activities. Check your network usage and consider reducing bandwidth-intensive activities.
• High Latency: The physical distance between your device and the DoH server can introduce significant latency. Servers geographically closer to you will generally result in faster response times. Consider using a DoH provider with servers located in your region.
• Firewall or Antivirus Interference: Your firewall or antivirus software might be interfering with your DoH connection. Temporarily disabling them (while ensuring your system is protected in other ways) can help determine if this is the cause. If it is, you may need to configure your security software to allow DoH traffic.
• DNS Configuration Errors: Incorrectly configured DoH settings in your operating system or browser can lead to slowdowns or connection failures. Double-check your settings to ensure they are accurately entered.
• Client-Side Issues: Problems with your device's network adapter, drivers, or even the browser itself could contribute to slower speeds. Update your drivers and try a different browser to rule out client-side issues.
• Underlying Network Problems: Issues like faulty network cables, router problems, or ISP outages can negatively impact all aspects of your network, including DoH.
• Poorly Performing DoH Provider: Not all DoH providers are created equal. Some might have better infrastructure or optimized routing than others. Trying an alternative provider could dramatically improve performance.

Troubleshooting Steps

1. Check Your Internet Connection

Start by ensuring your overall internet connection is stable and fast. Run a speed test (using a site like speedtest.net) to identify any broader connectivity issues.

2. Try a Different DoH Server

If your current DoH provider is overloaded or geographically distant, switch to a different one. Popular options include Cloudflare (https://cloudflare-dns.com/dns-query), Google Public DNS (https://dns.google/dns-query), and Quad9 (https://dns.quad9.net/dns-query). Note that each provider has different privacy policies; review those if you have privacy concerns.

3. Check Your DoH Configuration

Verify your DoH settings in your operating system and browser. Incorrectly configured settings can prevent DoH from working correctly or result in slow performance. Consult your device's or browser's documentation for instructions on setting up and verifying DoH.

4. Temporarily Disable Firewall/Antivirus

Temporarily disable your firewall and antivirus software to see if they are interfering with DoH. If this resolves the issue, configure your security software to allow DoH traffic through specific ports or URLs.

5. Update Network Drivers

Outdated network drivers can cause various connectivity problems. Update your network adapter drivers to the latest versions provided by your hardware manufacturer.

6. Try a Different Browser

Test DoH in a different browser to see if the problem is browser-specific. This can help identify if the issue lies with browser extensions, configurations, or the browser itself.

7. Use Command-Line Tools to Test DNS Resolution

Tools like nslookup or dig can be used to test DNS resolution times directly and help pinpoint network issues. These provide more detailed information than a simple browser-based speed test. Compare the resolution times between DoH and traditional DNS to identify any significant differences.

8. Contact Your ISP

If all else fails, contact your internet service provider (ISP). They can investigate possible network problems on their end affecting your DoH performance.

By systematically following these troubleshooting steps, you should be able to identify and resolve the cause of slow DoH performance, restoring your internet speed and maintaining the privacy benefits of DoH.