I don't think the plan is for it to be faster necessarily, but rather to move the existing tools off of a technology they are (slowly) moving away from. While t

I don't think the plan is for it to be faster necessarily, but rather to move the existing tools off of a technology they are (slowly) moving away from. While there will be some overhead due to the use of React I doubt it will be anything noticeable. In fact, I just checked it out in the Nightly version of Firefox and it doesn't feel any slower than the previous version of the debugger. As for the remote debugging protocol, I don't think that will really cost much of anything. The debugger itself is using Javascript so the deserialization cost of JSON is pretty much nonexistent on that end. As for everything needing to be written in HTML/CSS, this seems like an odd place to bring that up as this is quite literally a tool found inside of a web browser. As a whole though, I think HTML/CSS "apps" are cropping up largely because there are so many people familiar and comfortable with the technology, not because it's seen as more performant. And now that things like Electron and NW.js exist, it's trivial to leverage that knowledge to make a UI which uses it verses having to learn a new language/framework.