How to Harden Firefox (about:config Guide)

Step-by-step instructions to turn Firefox into a privacy powerhouse by disabling telemetry and enabling strict protections.

Why out-of-the-box Firefox isn't enough

Mozilla makes a great engine (Gecko), but to secure funding and market share, default Firefox comes with opt-out telemetry, Pocket integration, and default search deals. To get real privacy, we need to dig into about:config.

Step 1: The Settings Menu

  • Settings > Privacy & Security: Set Enhanced Tracking Protection to "Strict".
  • Settings > Privacy & Security: Uncheck "Send backlogged crash reports" and "Allow Firefox to send technical and interaction data to Mozilla".
  • Settings > Search: Change default search engine to DuckDuckGo, Brave Search, or Searx.

Step 2: Install uBlock Origin

Do not use AdBlock Plus or Ghostery. Install uBlock Origin. It is open source, highly efficient, and not compromised by the Manifest V3 changes affecting Chromium browsers.

Step 3: about:config tweaks (Advanced)

Type about:config in the URL bar, accept the risk, and search for these keys to toggle them:

privacy.resistFingerprinting = true
privacy.trackingprotection.enabled = true
browser.send_pings = false
network.dns.disablePrefetch = true
network.prefetch-next = false
webgl.disabled = true
Warning on privacy.resistFingerprinting

Setting this to true enables Tor-uplift patches. It is excellent for privacy, but it will lock your timezone to UTC, spoof your user-agent, and force a specific window size. Some websites will break. If you don't want to deal with breakage, use Brave instead.

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