Troubleshooting DNS over HTTPS (DoH) Issues in Firefox

DNS over HTTPS (DoH) enhances your online privacy by encrypting your DNS queries. If you're experiencing problems with DoH in Firefox, this guide will help you diagnose and resolve the issue.

Common Reasons Why DoH Isn't Working in Firefox

• DoH is not enabled: Firefox needs to be explicitly configured to use DoH. Check your settings.
• Incorrect DoH provider specified: You might have entered an incorrect or unavailable DoH server address.
• Network restrictions: Your network administrator might be blocking DoH traffic. This is common in corporate or school environments.
• Firewall interference: A firewall on your computer or network might be blocking DoH connections.
• Proxy server conflict: If you are using a proxy server, it might interfere with DoH functionality.
• Outdated Firefox version: Ensure you're using the latest version of Firefox for optimal compatibility.
• Conflicting extensions: Certain browser extensions might interfere with DoH. Try disabling extensions temporarily to see if it resolves the problem.
• DNS configuration conflicts: If you have other DNS settings configured (like a custom DNS server in your system settings), this may conflict with Firefox's DoH settings.

Troubleshooting Steps

1. Verify DoH is Enabled in Firefox

1. Type about:preferences#privacy in the Firefox address bar and press Enter.
2. Scroll down to the "Network Settings" section.
3. Under "DNS over HTTPS", ensure that "Use DNS over HTTPS" is enabled and that a DoH provider is selected (e.g., Cloudflare, Google Public DNS, or another provider you prefer).
4. If you're manually specifying a server, ensure the address is correct. Commonly used providers and their addresses are provided below. Incorrect addresses are a common source of problems.

Popular DoH Providers and their Addresses:

• Cloudflare: https://cloudflare-dns.com/dns-query
• Google Public DNS: https://dns.google/dns-query
• Quad9: https://dns.quad9.net/dns-query

2. Check Your Network Connection

Ensure your internet connection is stable and functioning correctly. Try accessing other websites to rule out broader internet connectivity problems.

3. Temporarily Disable Firewalls and Proxies

Temporarily disable any firewalls (like Windows Firewall or third-party firewall software) and proxy servers to see if they are blocking DoH. Remember to re-enable them afterward.

4. Update Firefox

Make sure you have the latest version of Firefox installed. Go to the Firefox menu (three horizontal lines), select "Help", and then click "About Firefox" to check for updates.

5. Disable Browser Extensions

Extensions can sometimes interfere with Firefox settings. Disable your extensions one by one to identify if any are causing the conflict.

6. Check Your System DNS Settings

Conflicts can arise if your operating system's DNS settings are configured differently from Firefox's DoH settings. Ensure your system-wide DNS settings are not explicitly set to another server, especially if using a public DNS server like Google DNS or Cloudflare DNS outside of Firefox.

7. Restart your Computer/Router

Sometimes a simple restart can resolve underlying network issues that may be interfering with DoH.

8. Advanced Troubleshooting (For Experienced Users)

If the above steps don't work, consider checking your network's firewall logs or contacting your network administrator for assistance if you're in a corporate or restricted network environment. You could also try using the Firefox developer tools to inspect network requests and look for errors related to DoH.

If you're still facing issues, please provide more details such as your operating system, network configuration, and any error messages you're encountering. This will help in providing more specific solutions.