These days, Mozilla is rewriting Firefox's devtools using a new and shiny technology stack. Anyone can join easily - the code is on Github, and it's just a matter of 2 commands in your terminal to get a local debugger running!
The debugger is universal - it can debug any browser, node and mobile. The feature list is innovative and aimed to be the best debugging experience for React, Angular, Ember, RxJS and more types of apps. In addition, making contribution to the debugger together with top notch developers from all around the world is an amazing experience!