Firefox

A browser setting covers that browser only. Other apps on the machine keep using the system’s DNS. Prefer the system-wide setup where you can; use this for a browser on a machine you do not control, or in addition.

1. Open Settings → Privacy & Security and scroll to DNS over HTTPS (or type about:preferences#privacy).

2. Choose Max Protection. (Increased Protection falls back to your system DNS when DoH fails, unfiltered and unidentified.)

3. Under Choose provider, select Custom and enter:

   https://dns.opdns.net/<profile-id>/<device>

   A device name such as laptop-firefox lets you tell the browser apart from the rest of the machine in logs.

   Screenshot to comeFirefox DNS over HTTPS settings with Max Protection selected and the opdns custom provider URL.

4. Check it works.

Firefox may turn DoH off by itself on networks that signal they filter DNS (the use-application-dns.net canary) unless Max Protection is set, and enterprise policies can lock the setting.

DNS-over-HTTPS: profile and device from the URL path

The first path segment is the profile id, the optional second one the device name: https://dns.opdns.net/<profile-id>/<device>. Every query carries both, so logs and analytics show this device by name wherever it connects from.

How identification works