How Do I Enable Java Applets in Firefox?

By Shea Laverty

When it's freshly installed, Mozilla's Firefox browser is automatically configured to support and activate JavaScript and Java applets everywhere you go. If your copy of Firefox has had JavaScript disabled or JavaScript blockers installed, however, it's a lot harder to enjoy your favorite websites to the fullest. How you enable JavaScript in Firefox depends on how it was disabled in the first place, but be careful -- globally enabling JavaScript can leave your computer at risk.


While JavaScript is enabled by default on Firefox, your network administrator may have disabled it for security reasons. To re-enable it, enter **about:config** in the address bar, and then press **Enter**. When prompted, click **I'll be careful, I promise!** to access the config screen. In the search bar, type **javascript.enabled** and look to see if the value is set to **True**. If it is, JavaScript is enabled. If it's set to **False**, double-click it to toggle it to **True**. Make sure you have your administrator's permission before pursuing this option.

Whitelisting in Java-Blocking Extensions

Firefox extensions like [NoScript](, [Ghostery]( and [Just Disable Stuff]( block all JavaScript and Java applets not on their whitelists. These extensions typically include a **Whitelist** or **Allow JavaScript** button for each website you visit, as well as a whitelist interface in their options in the **Add-Ons** menu to add websites by URL. Whitelisting a site allows all JavaScript and applets originating from that site.

Benefits of JavaScript

As Web development continues to advance, allowing JavaScript has increasingly become the best way to enjoy most of the features on websites. JavaScript enables tools like comment boards, interactive menus, Flash content like videos and games, and many other features. By disabling JavaScript, your experience of a website may be extremely limited, especially on sites that rely heavily on JavaScript in their construction. Disabling all JavaScript doesn't even remove the threat of all script-based attacks, only those based in JavaScript. Malicious XSS scripts and other hidden scripts can also pose a threat.

Risks of JavaScript

While JavaScript is often convenient and useful, it has a dark side. Many Web-based malicious attacks are JavaScript-based and attack your computer when you freely allow JavaScript. JavaScript is also used in trackers to monitor your surfing habits, and it is used to display advertisements and other annoyances. **Using a JavaScript blocking extension to limit JavaScript to only trusted websites is the only way to secure Firefox against JavaScript attacks, while allowing other safe JavaScript content**.