The fastest way to block a website in Firefox

Mozilla Firefox does not have a built-in website blocker in its main settings, but you can block sites using extensions (add-ons that add features to Firefox). The most straightforward approach is to install a free extension like uBlock Origin or LeechBlock NG, which let you type in website addresses you want to prevent from loading.

If you only need to block one or two sites occasionally, you can also use Firefox's parental controls feature, which is designed for restricting content but works for blocking specific addresses. For most people, an extension takes about two minutes to set up and gives you more control over what gets blocked and when.

Key Takeaways

  • Firefox extensions like uBlock Origin and LeechBlock NG are the standard way to block websites, and they work on Windows, Mac, and Linux.
  • You install an extension from Firefox's Add-ons page, then add website addresses to a blocklist inside the extension's settings.
  • Parental controls in Firefox can also block sites, but extensions give you more options and are easier to turn on and off.
  • Blocked sites will not load at all — you will see an error message instead of the webpage.

Installing an extension to block websites

Open Firefox and go to the Add-ons page by clicking the menu button (three horizontal lines) in the top right, then selecting "Add-ons and themes." Search for "LeechBlock NG" or "uBlock Origin" — both are free and widely used. Click the extension name, then click the blue "Add to Firefox" button.

Firefox will ask you to confirm. Click "Add" in the popup that appears. The extension will install in a few seconds, and you will see a small icon appear in your toolbar (usually in the top right of the browser window). You are now ready to add websites to your blocklist.

Adding websites to your blocklist

Click the extension icon in your toolbar. For LeechBlock NG, click "Options" or the gear icon to open the settings page. You will see a section labeled "Blocked sites" or "Sites to block." Type the website address in the text field — for example, facebook.com or reddit.com. Do not include "https://" or "www." unless you want to block only that exact version.

After you type the address, press Enter or click the button to save it. The site is now blocked. If you want to block multiple sites, add them one at a time, each on its own line. You can test a blocked site by trying to visit it in a new tab — you should see a message saying the site is blocked instead of the normal webpage.

Using Firefox's parental controls to block sites

If you prefer not to install an extension, Firefox has a built-in parental controls feature that can block websites. Open Firefox settings by clicking the menu button and selecting "Settings." Go to the "Privacy & Security" tab on the left side.

Scroll down to the "Parental Controls" section and check the box next to "Enable Parental Controls." A new section will appear where you can enter website addresses you want to block. Type the address and press Enter to add it to the blocklist. This method works the same way as an extension but is built into Firefox itself.

Blocking sites on a schedule with extensions

Some extensions let you set times when sites are blocked. LeechBlock NG, for example, has an "Access times" feature where you can say "block this site between 9 AM and 5 PM on weekdays" or "block it all day on Sundays." This is useful if you want to prevent access during work hours or study time but allow it at other times.

To set up scheduled blocking in LeechBlock NG, open the extension options, find the site you want to block, and look for the "Access times" section. You can set different schedules for different days of the week. The extension will automatically enforce the schedule — the site will be blocked during the times you set and accessible outside those times.

Removing a blocked website or turning off blocking

If you change your mind about a blocked site, you can remove it from your blocklist. Click the extension icon, open the settings, find the site in your blocked sites list, and click the delete or remove button next to it. The site will be unblocked immediately.

If you want to turn off blocking entirely without removing individual sites, you can disable the extension by clicking the menu button, going to "Add-ons and themes," finding the extension, and clicking the toggle switch to turn it off. The extension will stay installed but will not block anything until you turn it back on.

What happens when you try to visit a blocked website

When you navigate to a blocked site, Firefox will not load the webpage. Instead, you will see a message from the extension saying the site is blocked. The message usually includes the name of the site and the reason it is blocked (if you added a note when you created the blocklist).

Some extensions let you temporarily unblock a site for a set amount of time — for example, "allow this site for 30 minutes" — without removing it from your permanent blocklist. This is helpful if you need to visit a blocked site occasionally but want the block to resume automatically.

Frequently Asked Questions

Can I block a website on Firefox without using an extension?

Yes, Firefox's built-in parental controls feature can block sites without an extension. Go to Settings, find Parental Controls, enable it, and add website addresses to the blocklist. Extensions give you more options, but parental controls work if you prefer not to install add-ons.

Will a blocked website still load if I use a VPN?

No. Website blocking in Firefox happens on your browser, not on your internet connection, so a VPN will not bypass it. The extension blocks the site before Firefox even tries to connect to it.

Can I block a website on my phone version of Firefox?

Firefox on Android and iPhone supports some extensions, but not all blocking extensions are available for mobile. Check the Firefox Add-ons page on your phone to see which blockers are compatible with your device.

What is the difference between uBlock Origin and LeechBlock NG?

uBlock Origin is primarily an ad blocker but can block entire websites. LeechBlock NG is designed specifically for blocking sites and has more scheduling options. Both are free. Choose LeechBlock NG if you want scheduled blocking; uBlock Origin if you want a simpler, lighter extension.

If I block a website, can someone else using my Firefox account see that it is blocked?

Yes. Your blocklist is stored in your Firefox profile, so anyone who logs into your Firefox account on any device will see the same blocked sites. If you share a computer, create a separate Firefox profile for other users.