The internet is full of unwanted content, so you may want to restrict access to certain sites. While there isn’t a feature built into Mozilla Firefox to block websites, there are extensions that will get the job done.

Block a website in Firefox on a desktop

To block a website in Firefox on your desktop or Mac computer, open Firefox and navigate to Mozilla official site for add-ons. In the search bar in the upper right corner of the window, type “Block site”. Select the first item in the search results.

Click on

On the next page, you will see information about the extension, including the name of the developer and a brief description of the extension. Click on “Add to Firefox”.

Click on

A message appears asking you to add the blocking site. It is basically asking your permission to:

  • Access your data for all websites
  • Show notifications
  • Go to your browser tabs (in this case, only in Mozilla Firefox)

Click on “Add”.

Another message appears, confirming that the Block Site extension has been added to Firefox. You can also check the box next to the option “Allow this extension to run in private windows” if you want to enable it.

When you’re done, click “OK, get it.”

Click on

Now that the extension is added to Firefox, you can manage its settings. Click the hamburger menu at the top right to display the browser menu, then click “Add-ons”.

Click on the hamburger menu, then click

You can also access Firefox add-ons by pressing Ctrl + Shift + A (Command + Shift + A on Mac), or by typing “about: addons” in the address bar.


In the left pane, click on “Extensions”.

A list of your installed extensions will appear. Find “Block site” and click on the three dots next to it.

Click on the three dots next to

Select “Options” from the menu that appears.

Click on

On the next page, enter the name of the website you want to block in the “Block new hostname” text box. Click “Add” to add the website to the block list.

You can also set a schedule to block the website. This is handy if you don’t want your kids on Facebook after a while on school nights, for example.

Type the website you want to block in the text box, click

Click “Save” in the “Tools” section to save your changes. You can make sure that your settings cannot be changed if you set a master password.

Now, whenever someone tries to access the blocked list websites, they will see the message below.

The message

Block a website in Firefox on mobile

The process of blocking a site in Firefox is a little different on your iPhone, iPad, Where Android device. Android offers a little more flexibility than iOS and iPadOS. You can download a free add-on for Android called Leechblock NG. It has mostly positive reviews and is Firefox specific, which means it won’t restrict sites in other browsers, like Google Chrome.

After installing Leechblock NG, you just need to add the sites you want to block to the block list.