7 Hidden Firefox Settings I Always Enable
Introduction
I've been using Firefox as my main browser for years. Every time I reinstall my system or set up a new device, the first thing I do isn't installing extensions – it's tweaking a few default settings. They won't turn Firefox into a different browser, but they make everyday browsing much more comfortable. Some of these options are buried deep, and if no one points them out, you might never discover them.
I used to follow those "50 Firefox settings you must change" guides and modify every single item, only to find that most of them made no noticeable difference. What I've kept over time are just a handful of options that actually affect my daily experience. This article is about the 7 settings I always enable on a fresh Firefox install – and I hope they're useful to fellow Firefox users.
1. Enable the Rust Ad‑Blocking Engine
Starting with Firefox 149, the browser quietly added a new feature – an ad‑blocking engine written in Rust, based on Brave's adblock‑rust project. The biggest advantage of this engine is performance: after Brave switched to adblock‑rust, memory consumption dropped by 75% compared to its previous engine. Rust is known for its memory safety and high performance, making it more efficient and stable when handling complex ad‑filtering rules.
Currently, this engine is disabled by default and has no user interface. Enabling it is simple: go to about:config, search for privacy.trackingprotection.content.protection.enabled, and double‑click to set it to true. Then search for privacy.trackingprotection.content.protection.test_list_urls and enter the URLs of the filter lists you want, separated by a pipe character. I usually add EasyList and EasyPrivacy as the core rules.
After enabling it, you might not notice a huge difference in everyday browsing, but on complex pages with lots of ads and trackers, the browser feels noticeably snappier.
2. Turn on HTTPS‑Only Mode
This setting forces all connections to use encrypted HTTPS. By default, Firefox tries HTTPS first but falls back to HTTP if a site doesn't support it. HTTPS‑Only Mode is stricter – if a site doesn't support HTTPS, it blocks the connection and shows a warning.
This is especially useful on public Wi‑Fi. HTTP connections are transmitted in plain text, so anyone on the same network can intercept your browsing data. With HTTPS‑Only Mode on, all your data is encrypted, giving you a much higher level of security. You can find it in Settings → Privacy & Security → HTTPS‑Only Mode, and choose "Enable HTTPS‑Only Mode in all windows".
3. DNS over HTTPS
Traditional DNS queries are also sent in plain text, so your ISP can see which websites you're visiting. DNS over HTTPS (DoH) encrypts these queries, preventing third parties from easily snooping on your browsing history.
In Firefox, DoH is under Settings → General → Network Settings – check "Enable DNS over HTTPS". The default provider is Cloudflare, but you can also use NextDNS or other custom providers. If you care about privacy, or simply don't want your ISP logging your browsing activity, this setting is worth turning on.
4. Total Cookie Protection
This is part of Firefox's Enhanced Tracking Protection and is enabled by default in Standard mode. It works by giving each website its own separate "cookie jar" – cookies from site A can't be accessed by site B. Previously, third‑party trackers could follow you across different sites using cookies; Total Cookie Protection blocks that completely.
If it's been disabled for some reason, you can check about:config and search for network.cookie.cookieBehavior – make sure its value is 5. I wouldn't recommend changing it to 4 or other values, as that would weaken privacy protection.
5. Disable Pocket (If You Don't Use It)
Pocket is Firefox's built‑in "read‑it‑later" feature, with entries in the address bar and the new tab page. If you never use it, it only clutters the interface. I prefer a clean browser, so I always turn it off.
In about:config, search for extensions.pocket.enabled and double‑click to set it to false. After that, the Pocket button in the address bar disappears, and the new tab page stops recommending Pocket articles.
6. Disable Telemetry and Data Collection
By default, Firefox collects technical and interaction data to help Mozilla improve the browser. This data is anonymous and doesn't affect ordinary users. But if you, like me, prefer not to have software silently uploading data in the background, you can turn it off.
Go to Settings → Privacy & Security, scroll down to "Firefox Data Collection and Use", and uncheck "Allow Firefox to send technical and interaction data to Mozilla". You can also fine‑tune this in about:config, but for most users, turning it off in the Settings panel is enough.
7. Tweak Tab Behavior
There are a few tab‑related settings I tweak out of personal habit.
In about:config, search for browser.ctrlTab.sortByRecentlyUsed – set it to true, and Ctrl+Tab will cycle through tabs in most‑recently‑used order rather than left‑to‑right. Another one is browser.tabs.loadInBackground, which is true by default, meaning new tabs load in the background. If you prefer that content loads when you switch to the tab, keep the default; if you'd rather save resources by loading only when you switch, set it to false.
These tweaks are subtle, but once you get used to them, going back to the defaults feels awkward.
Which Settings Should You Leave Alone?
There are plenty of articles out there with "100 Firefox settings you must change", listing tons of about:config parameters. I've tried some of them, and honestly, most made no noticeable difference – some even caused compatibility issues. Don't enable every optimisation just to gain a slight speed boost – many so‑called "optimisations" are meaningless.
The ones I stick with are the few listed above. Some settings aren't objectively right or wrong – they just match my habits. If you're already comfortable with Firefox's defaults, you don't necessarily need to follow all of them.
Alternatives and Further Reading
If you're interested in customising Firefox further, these are also worth exploring: Betterfox – a collection of Firefox optimisations; uBlock Origin – the most powerful ad blocker; Firefox Multi‑Account Containers – isolate sessions by account; Sidebery – sidebar tab management; and Auto Tab Discard – automatically free memory from background tabs.
Final Thoughts
It takes just a few minutes to apply all these settings, but they make Firefox feel more tailored to how I browse. Privacy is stronger, the interface is cleaner, and ad blocking is faster – for me, that's already enough. If you're a Firefox user too, feel free to pick a few and give them a try.
