I'd like to add that the Firefox DevTools are excellent now. For a long time there was this weird stuff with built-in devtools but-you-still-kinda-needed-FireBug and it was a mess (a sufficiently big mess to keep me on a random Blink-based browser), but these days it's just great.

Firefox is a truly great browser, they really made amazing improvements on all fronts in the last years. And I say this as someone who never used Firefox as their daily driver until half a year ago or so.