The Firefox Developer Tools team has been working hard over the last two years to provide web developers with useful, performant developer tools in Firefox. The tools are now excellent and recieving a lot of attention from web developers. We have always thought that in addition to being useful and performant, in order to be Firefox they also need to be extensible so that add-on hackers and web developers can create their own customized tools and provide better support for specific web frameworks and technologies. This talk will cover the current apis and techniques used to extend the developer tools, how to get started, where to find help and real-world examples.