Firefox's default settings are reasonable for general users. For anyone who cares about privacy, performance, or how the browser handles specific behaviors, there are specific settings worth changing.
This is not a comprehensive list — it is the settings that most change how the browser feels and behaves.
Privacy settings
Enhanced Tracking Protection (ETP)
Settings → Privacy & Security → Enhanced Tracking Protection
Default: Standard. Consider switching to Strict mode. Strict mode blocks more trackers, including cross-site tracking cookies and fingerprinting scripts. Some sites may break (usually sites that require cross-site cookies for login persistence). The tradeoff is usually worth it.
DNS over HTTPS (DoH)
Settings → Privacy & Security → DNS over HTTPS
Default: Off in many regions. Consider enabling with a privacy-focused resolver like Cloudflare (1.1.1.1) or NextDNS. DoH encrypts your DNS queries, preventing your ISP from seeing which domains you visit.
Sending technical data to Mozilla
Settings → Privacy & Security → Firefox Data Collection and Use
Uncheck "Allow Firefox to send technical and interaction data to Mozilla." Personal preference; the data helps improve Firefox, but if you prefer not to share, it is straightforward to disable.
Performance settings
Hardware acceleration
Settings → General → Performance → Use recommended performance settings
Uncheck this and enable hardware acceleration manually if Firefox feels slow on video-heavy sites. Some graphics drivers conflict with hardware acceleration; if you experience crashes or glitches on video, try disabling it here.
Content process limit
In about:config: dom.ipc.processCount — this controls how many content processes Firefox uses. Modern hardware benefits from 8-16 processes; older machines may work better with fewer.
Interface settings
Compact mode
Settings → General → Density → Compact. Reduces the height of the toolbar and tabs, giving more vertical space to page content. No functional change, just more screen real estate.
Tab scroll
In about:config: browser.tabs.tabMinWidth — set to 0 to prevent tabs from getting cut off at minimum size; Firefox will shrink them and show them all instead of overflowing.
Extensions worth installing alongside these settings
After tightening Firefox's privacy settings, these extensions complete the picture:
uBlock Origin — blocks ads and trackers at the network level. The settings above reduce what trackers can read; uBlock blocks them from loading at all.
NightOwl — dark mode on all websites with auto-scheduling. Install
AI Writing Assistant — if you want grammar checking without sending text to a third party. Install
NightOwl and AI Writing Assistant are two of 11 Firefox extensions I built — see the full series.
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