It's been available in Chrome for a year and a half.. https://plus.google.com/u/0/+AddyOsmani/posts/PmTC5wwJVEc ..this is actually one of the things that's most annoying about web dev - each browser has some really cool stuff for debugging, but none of them has everything. The Firefox team are addressing that though - https://hacks.mozilla.org/2014/09/firefox-tools-adapter/ - Firefox nightly can connect to Chrome's debugging interface so you can use Firefox's toolset to debug a page in Chrome. Which is insanely cool.