The tilde prefix (~) can be used to restrict blocking to pages that contain given keywords. Within a keyword you can use an asterisk (*) to match any number of characters (except whitespace) and an underscore (_) to match whitespace. Note that the keyword matching is case-insensitive (i.e., uppercase and lowercase are treated as equivalent).

So, for example, you could enter the following into the list of sites:

somesite.com
anothersite.com
~anteaters
~crypto*
~*alicious
~green_eggs_and_ham

This would result in pages on the sites somesite.com and anothersite.com being blocked only when those pages contain the complete word “anteaters” or any word beginning with “crypto” or any word ending with “alicious” or the complete phrase “green eggs and ham”.

If you want to block pages on any website that contain given keywords, you’ll need to use wildcards to specify all websites. For example:

*
~justin_bieber
~kim_kardashian

If you want pages with the specified keywords to be allowed rather than blocked, you should select the option Treat keywords as allow-conditions rather than block-conditions under Advanced Options. Thus, if you were to select that option with the example above, the effect would be to block all pages except those containing “justin bieber” or “kim kardashian” (not something I recommend, just for the record).

Note: LeechBlock looks for keywords only in the title or text of a webpage, not in the URL. If you want to block URLs containing keywords, you can do so like this:

somesite.com/**somekeyword
somesite.com/**anotherkeyword

The Load list of sites from URL field allows you to obtain the list of sites to block from a URL (e.g., a text file on a web server). The list will be loaded when the browser is first started and also when the options are changed. This feature is useful if you have LeechBlock installed on multiple machines and want to avoid having to update the settings on each machine in turn whenever you need to change the list of the sites to block. (Note also that if you put $S in the URL it will be replaced with the number of the block set and $T will be replaced with a UTC timestamp in milliseconds. The latter can be useful for avoiding caching problems.)

Note that Firefox’s security model doesn’t allow extensions to load local files (even with the file:// protocol). As a workaround, you can use Dropbox:

• Copy your text file with the list of sites into a Dropbox folder and share the file.
• Copy the download link to the file into the Load list of sites from URL field, replacing www.dropbox.com with dl.dropboxusercontent.com.

Alternatively, you can use Google Drive to host the text file, as long as you use a direct download link rather than the regular share link.

If you don’t understand any of this then you almost certainly don’t need it! If in doubt, just leave the Load list of sites from URL field blank.

The options are disabled because you selected the option Prevent access to options for this block set at times when these sites are blocked and now those sites are blocked (hence the options are currently inaccessible). The purpose of this option is to allow users to prevent themselves from easily changing the settings once the sites have been blocked, but in a way that doesn’t prevent access to all LeechBlock options.

If you really need to change the settings for the block set before the blocking period has ended, you can email leechblockng@proginosko.com for instructions, specifying which browser you’re using (Firefox, Chrome, etc.).

Email leechblockng@proginosko.com for instructions on how to reset your password, specifying which browser you’re using (Firefox, Chrome, etc.).

Starting with Firefox 57, which will be released in November 2017, only extensions built with the WebExtensions framework will be work in Firefox (see here for details). After investigating what it would take to modify the existing LeechBlock extension to use only WebExtensions, I concluded it would be easier and better to rewrite the extension from the bottom up, reusing existing code wherever possible.

The new extension is called LeechBlock NG (Next Generation). Go here to install the latest version.

If you want to transfer your settings to the new version, export them to a text file before you uninstall the legacy version (Options > General > Export Options). You can then import them into the new version once you’ve installed it.

The source code for LeechBlock NG is available on GitHub. Please post bug reports there!

You can find all versions of LeechBlock listed here, including pre-release/beta versions which are signed but have not been reviewed and approved by the Mozilla Add-ons team. Install the latter at your own risk!

Not exactly. However, if you put the # character before any entry in the list of sites it will be ignored. This can be useful for temporarily deactivating entries in the list. (Note that any entries starting with # will be moved to the top of the list, because LeechBlock stores the list in alphanumerical order.)

Yes. Go to Options and enter (or copy/paste) the full URL of the page into the first field of the “How to Block” section of the relevant block set.

Yes: https://www.tapatalk.com/groups/leechblock/

There are several ways of doing this on Windows. (If anyone knows of any solutions for Linux or MacOS, please pass them on to me!)

On Windows, if you’re not a member of the Administrators or Power Users groups then (by default) you shouldn’t be able to change the system clock anyway. If you are able to change the clock, you could try one of these solutions:

Solution #1: Hide the clock from the Taskbar

Right-click on the Taskbar, select Properties, and uncheck the option Show the clock. Easy to undo, of course, but adds an extra layer of inconvenience.

Solution #2: Change the permissions using the Group Policy Editor

• Select Run… from the Start Menu (or press Windows+R) and enter gpedit.msc as the program to open.
• Navigate to Computer Configuration / Windows Settings / Security Settings / Local Policies / User Rights Assignment.
• Edit the policy for Change the system time and remove the Administrators and Power Users groups from the list (i.e., empty the list).
• Log off and log on again for the new permissions to take effect.

You can restore the original permissions by re-editing the policy and adding the Administrators and Power Users groups back to the list.

Note that the Group Policy Editor is not included in the Home Edition of Windows XP, Vista, and 7, in which case you could try…

Solution #3: Use an elevated command prompt

Go here for detailed instructions (scroll down to “Option Two”).

Solution #4: Use third-party software Clock Guard

I’ve never used Clock Guard and I can’t vouch for it, but it may do the job for you.