Add-ons are small pieces of software that enhance the way Firefox works and change the way Firefox looks. According to the latest figures, add-ons are quite popular with Firefox users from all corners of the globe.

Mozilla just announced that Firefox add-ons hit 4 billion downloads. Or to put it in other words, Mozilla's official site for add-ons served more than 4 billion add-ons to Firefox users who wanted to customize, enhance and improve their Firefox copy.

4 billion add-on downloads is an impressive milestone.

Here are some other figures that are equally impressive:

• 18,000 add-ons are available for download.
• 369,000 browser themes are available to change the way Firefox looks.
• Grateful Firefox users donated $634,000 to add-on developers (that’s since 2009, when Mozilla started keeping records).

Visit addons.mozilla.org, commonly known as "AMO", to get add-ons for Firefox, to check the latest add-on releases, or to see what add-ons are popular among Firefox users.

Visit the themes section on AMO to find interesting themes for Firefox.

In related news, you may want to know that Mozilla recently updated the Firefox web browser to version 35. This updated version makes it easier to use Firefox Hello (a global communications system that is built directly into the Firefox web browser), lets you share content through a multitude of social networks (view all available social services on the Share Activation page), and lets you check out the Firefox Marketplace Beta.

Additional information about Firefox 35 is available here.

In further related news, Firefox 36 is scheduled to graduate from Beta on February 24, 2015.