Firefox extensions are a great way to customize your browsing experience. They can help you become more productive, stay secure, and get the most out of Firefox. With extensions, you can add new features to Firefox, change the way web pages look and function, and even block ads. Developers can create and share their own extensions to make Firefox even better. With the Firefox Add-ons Marketplace, developers can easily share their extensions with the world. It's a great way to show off your skills and give Firefox users a better experience. And best of all, it's free and open source!