5 Underrated Firefox Extensions That Actually Respect Your Privacy

The extension ecosystem is full of tools that claim to help you while quietly sending data to third-party servers. These five actually keep data local — and the ones I've tried, I can vouch for personally.

1. Weather & Clock Dashboard

Install from AMO

Replaces your new tab with live weather, a 3-day forecast, and configurable world clocks. The privacy angle: weather data comes from Open-Meteo (no API key, no account), your coordinates never leave your browser, and the entire extension is ~500 lines of vanilla JS/CSS you can read in an afternoon.

No analytics. No telemetry. No external fonts or CDN assets. Just weather.

What I checked: Source code is MIT licensed, and AMO's review process verified no remote code execution or unnecessary permissions.

2. uBlock Origin

Install from AMO

The gold standard for content blocking. Open source (GPLv3), completely local rule evaluation — nothing about your browsing leaves your machine. The filter lists update locally; the extension never phones home about what sites you visit.

3. LocalCDN

Install from AMO

Intercepts requests to CDNs (Google Fonts, jQuery CDN, Bootstrap CDN) and serves them from local cache instead. This breaks the tracking vector where CDN providers log which sites you visit by watching resource requests.

4. Cookie AutoDelete

Install from AMO

Automatically deletes cookies when you close a tab. Completely local — no sync, no cloud, no telemetry. The extension stores its whitelist in browser.storage.local only.

5. Firefox Multi-Account Containers

Install from AMO

Mozilla's own extension. Isolates cookies and site data per container, preventing cross-site tracking. All state is local. The container configuration syncs through Firefox Sync (encrypted, if you use it) but nothing goes to third parties.

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What to look for in a privacy-respecting extension

When evaluating any extension:

1. Check permissions on AMO — does it ask for tabs, webRequest, <all_urls>? Those are broad and worth scrutinizing.
2. Look for external requests — does the extension's manifest.json list any content_security_policy or host_permissions to external domains?
3. Read the AMO review notes — Mozilla's team flags anything suspicious
4. Check if it's open source — not a guarantee, but auditable code is better than a black box

All five extensions above pass these checks. Your new tab, your data.

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Disclosure: I built Weather & Clock Dashboard. The others are just extensions I use.