LeechBlock NG

LeechBlock NG is a free, open-source browser extension for Firefox (and Chrome/Edge) that blocks specified sites on a configurable schedule, with up to 6 independent block sets and a lockdown mode that prevents settings from being changed during active block periods. As of May 2026, it is the most capable free distraction blocker available for Firefox users.

At a glance

Field	Value
Pricing	Free (open source, forever)
Platforms	Firefox, Chrome, Edge
Mobile	No
Lockdown mode	Yes — blocks settings changes during active periods
Last verified	May 20, 2026

What LeechBlock NG does well

• Zero cost, full capability. No “free tier.” No upgrade prompts. Every feature — multiple block sets, scheduling, lockdown mode, custom delay pages — is available from day one.
• Six block sets. Set A blocks Reddit on weekday mornings. Set B blocks news sites after 9 PM. Set C limits YouTube to 30 minutes per day on weekends. The flexibility covers almost any blocking strategy without needing multiple extensions.
• Real lockdown. Enable “Lock down access to LeechBlock options” on a block set and the settings panel becomes inaccessible during that block. This is the key differentiator from lightweight blockers that you can simply pause.
• Schedule granularity. Block from 09:00–12:00 Monday–Friday only. Or Saturday and Sunday only. Or every day except Wednesday. Or with a countdown timer. The scheduler handles uncommon patterns well.

What LeechBlock NG doesn’t do

• No app-level blocking. LeechBlock only blocks sites in the browser. It has no effect on native apps. For that, use Freedom or Cold Turkey.
• No cross-device sync. Each browser install is independent. If you need the same blocklist across a work and personal machine, you’ll reconfigure manually.
• Not the best on Chrome. The Firefox version is the reference implementation. Chrome’s extension architecture limits a few LeechBlock features. If you’re primarily a Chrome user, Cold Turkey or StayFocusd may serve better.

Best for

Firefox users who want a schedule-based, genuinely unbypassable (when lockdown is enabled) free site blocker with no subscription. The go-to free alternative to Freedom for browser-level blocking.

Setup in 5 minutes

1. Install LeechBlock NG from the Firefox Add-ons page.
2. Click the toolbar icon → Options.
3. Block Set 1: Name it, add your sites to the block list (one per line).
4. Set your schedule: tick the days, set the time window (e.g. 09:00–17:00).
5. Under Access, check “Lock down access to LeechBlock options during blocked periods.”
6. Save. Reload a blocked site to confirm it’s active.

Alternatives

• Freedom — paid ($39.99/yr on sale), but cross-device and covers mobile. The right choice when the problem follows you from browser to phone.
• Cold Turkey — $39 one-time, Mac + Windows desktop, stricter system-level blocking. Better for desktop users who want beyond-browser coverage.
• SelfControl — free Mac app with an unbypassable timer. No schedule, but truly system-level.