Firefox Security Settings: What They Do and How to Harden Them
Firefox ships with robust security defaults, but understanding them helps you make informed decisions about what to keep, what to change, and what to add. What Firefox Protects by Default HTTPS-First Mode (Firefox 83+) Firefox now tries HTTPS first for every connection. When you type a domain without specifying http://, Firefox upgrades to HTTPS automatically. If the site doesn't support HTTPS,…
Firefox comes with strong security settings enabled by default. When you open a website without specifying the "http://" prefix, Firefox automatically upgrades it to "https://" if the site supports it. If a site does not support HTTPS, Firefox connects via HTTP and shows a visual warning in the address bar.
To check if HTTPS-Only Mode is enabled, navigate to Settings > Privacy & Security > HTTPS-Only Mode and enable it. This feature forces all connections to use HTTPS.
Firefox's Enhanced Tracking Protection (ETP) safeguards users by blocking social media trackers, cross-site tracking cookies, cryptominers, fingerprinters, and tracking content. The default setting is Standard, but for improved protection against site breakage, the Strict mode can be selected. Firefox maintains its own root certificate store separate from the operating system, ensuring that corporate proxy MITM certificates must be explicitly added rather than being automatically trusted.
Firefox uses a multi-process architecture with OS-level sandboxing to isolate processes such as content, media, and GPU. The level of isolation depends on the operating system; Linux uses seccomp-BPF, while Windows utilizes the Windows sandbox. To verify the sandbox status, go to about:support > Security.
In the about:config section, you can customize security settings. Adjust the security.tls.version.min to enable the minimum TLS version allowed, typically set to 3 (TLS 1.2) by default. Increasing it to 4 (TLS 1.3 only) will block connections to older servers. The security.mixed_content.block_active_content and security.mixed_content.block_display_content settings control how Firefox handles mixed content on HTTPS pages. Lastly, the dom.security.https_only_mode setting is equivalent to the UI HTTPS-Only Mode setting.
While Firefox's security settings are robust, users can further enhance their security by installing extensions like uBlock Origin for content blocking, Firefox Multi-Account Containers for isolating sites, and local CDN servers like Decentraleyes to prevent tracking through CDN usage patterns. However, it is essential not to disable JavaScript universally or use multiple anti-fingerprinting extensions, as they may break functionality or make the browser more identifiable.
Instead, users should choose one approach for privacy resist fingerprinting or utilize dedicated extensions.
Written by urgent.news from Dev.to's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
