}
 }
 ```
+### WebsiteFilter
+Blocks websites from being visited. The parameters take an array of Match Patterns, as documented in https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Match_patterns. Only http/https accesses are supported at the moment. The arrays are limited to 1000 entries each.
+```
+{
+  "policies": {
+    "Block": ["<all_urls>"],
+    "Exceptions": ["http://example.org/*"]
+  }
+}
+```
 
       <string id="SanitizeOnShutdown_Explain">If this policy is enabled, all data is cleared when Firefox is closed. This includes Browsing & Download History, Cookies, Active Logins, Cache, Form & Search History, Site Preferences and Offline Website Data.
 
 If this policy is disabled or not configured, data is not cleared when the browser is closed.</string>
+      <string id="WebsiteFilter_Block">Blocked websites</string>
+      <string id="WebsiteFilter_Block_Explain">If this policy is enabled, you can specify match patterns that indicate sites to be blocked. The match patterns are documented at https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Match_patterns. Only http/https accesses are supported at the moment. There is a 1000 entry limit.",
+
+If this policy is disabled or not configured, no websites are blocked.</string>
+      <string id="WebsiteFilter_Exceptions">Exceptions to blocked websites</string>
+      <string id="WebsiteFilter_Exceptions_Explain">If this policy is enabled, and the website filter is enabled, you can specify match patterns for sites you do not want to block. The match patterns are documented at https://developer.mozilla.org/en-US/Add-ons/WebExtensions/Match_patterns. Only http/https accesses are supported at the moment. There is a 1000 entry limit.",
+
+If this policy is disabled or not configured, there are no exceptions to the website filter.</string>
       <string id="Bookmark1">Bookmark 1</string>
       <string id="Bookmark2">Bookmark 2</string>
       <string id="Bookmark3">Bookmark 3</string>
       <presentation id="Extensions">
         <listBox refId="Extensions"/>
       </presentation>
+      <presentation id="WebsiteFilter">
+        <listBox refId="WebsiteFilter"/>
+      </presentation>
       <presentation id="Permissions"><listBox refId="Permissions"/></presentation>
       <presentation id="PopupsAllow"><listBox refId="PopupsAllowDesc">Allow popups for websites</listBox></presentation>
       <presentation id="Cookies_AcceptThirdParty">
 
         </enum>
       </elements>
     </policy>
+    <policy name="WebsiteFilter_Block" class="Both" displayName="$(string.WebsiteFilter_Block)" explainText="$(string.WebsiteFilter_Block_Explain)" key="Software\Policies\Mozilla\WebsiteFilter\Block" presentation="$(presentation.WebsiteFilter)">
+      <parentCategory ref="firefox"/>
+      <supportedOn ref="SUPPORTED_WINXPSP2"/>
+      <elements>
+        <list id="WebsiteFilter" key="Software\Policies\Mozilla\Firefox\WebsiteFilter\Block" valuePrefix=""/>
+      </elements>
+    </policy>
+    <policy name="WebsiteFilter_Exceptions" class="Both" displayName="$(string.WebsiteFilter_Exceptions)" explainText="$(string.WebsiteFilter_Exceptions_Explain)" key="Software\Policies\Mozilla\WebsiteFilter\Exceptions" presentation="$(presentation.WebsiteFilter)">
+      <parentCategory ref="firefox"/>
+      <supportedOn ref="SUPPORTED_WINXPSP2"/>
+      <elements>
+        <list id="WebsiteFilter" key="Software\Policies\Mozilla\Firefox\WebsiteFilter\Exceptions" valuePrefix=""/>
+      </elements>
+    </policy>
   </policies>
 </policyDefinitions>