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Firefox DNS Settings Explained
Firefox handles DNS differently from most browsers. Unlike Chrome or Edge, which typically rely on the operating system's DNS configuration, Firefox can manage its own DNS resolution independently. This means Firefox can bypass your system-level DNS settings entirely — including those set by your VPN.
By default, Firefox routes DNS queries through the operating system. However, when DNS over HTTPS (DoH) is enabled, Firefox sends queries directly to a DoH provider (Cloudflare by default), bypassing your system resolver. This is a double-edged sword: it improves privacy against local network snooping, but it can conflict with VPN configurations that route DNS through their own servers.
DNS over HTTPS in Firefox
Mozilla was one of the first browser vendors to implement DNS over HTTPS. When enabled, every DNS lookup Firefox makes is encrypted and sent to a trusted resolver. This prevents your ISP, network administrator, or anyone on the same WiFi network from seeing which domains you're requesting.
Firefox offers three DoH modes: off (uses system DNS), default protection (uses DoH when available but falls back to system DNS), and max protection (only uses DoH, fails if unavailable). For the strongest privacy, use max protection with a trusted provider — but be aware this may bypass your VPN's DNS servers. If you're using a VPN, check whether your provider recommends keeping DoH on or off.
How to Check and Fix DNS Leaks in Firefox
- Open Firefox and go to Settings → Privacy & Security.
- Scroll down to DNS over HTTPS.
- Choose your preferred protection level and select a trusted provider such as Cloudflare or NextDNS.
- If you use a VPN with its own DNS, consider setting DoH to "Off" so your VPN handles all DNS queries.
- Run our free DNS Leak Checker to verify no leaks remain.
Firefox can also expose your real IP through WebRTC. Learn how to prevent this in our Firefox WebRTC leak fix guide. For general DNS leak fixes across all platforms, see our step-by-step DNS leak fix guide.
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