diff --git a/README.md b/README.md
index 4484c51..832a315 100644
--- a/README.md
+++ b/README.md
@@ -10,9 +10,9 @@ YouTube Review:
 
 Download Links:
   * Chrome: https://chrome.google.com/webstore/detail/user-agent-switcher-and-m/bhchdcejhohfmigjafbampogmaanbfkg
-  * Firefox: https://addons.mozilla.org/en-US/firefox/addon/user-agent-string-switcher/
+  * Firefox: https://addons.mozilla.org/firefox/addon/user-agent-string-switcher/
   * Edge: https://microsoftedge.microsoft.com/addons/detail/useragent-switcher-and-m/cnjkedgepfdpdbnepgmajmmjdjkjnifa
-  * Opera: https://addons.opera.com/en/extensions/details/user-agent-switcher-8/
+  * Opera: https://addons.opera.com/extensions/details/user-agent-switcher-8/
 
 Usage Instruction:
   * https://add0n.com/useragent-switcher.html
diff --git a/extension/firefox/common.js b/extension/firefox/common.js
index e9e80ac..bcf2ad1 100644
--- a/extension/firefox/common.js
+++ b/extension/firefox/common.js
@@ -333,7 +333,7 @@ const ua = {
         const o = ua.object(null, windowId, tab.cookieStoreId);
         chrome.browserAction.setBadgeText({
           tabId,
-          text: o && o.platform ? o.platform.substr(0, 3) : ''
+          text: o && o.platform ? o.platform.slice(0, 3) : ''
         });
       }));
     }
@@ -341,7 +341,7 @@ const ua = {
       const o = ua.object(tabId, undefined, cookieStoreId);
       chrome.browserAction.setBadgeText({
         tabId,
-        text: o.platform ? o.platform.substr(0, 3) : 'BOT'
+        text: o.platform ? o.platform.slice(0, 3) : 'BOT'
       });
     }
   },