"In terms of incompatibilities they're about as different as Gecko is from Blink, if not more so." > Not sure how familiar you are with the history of browser

"In terms of incompatibilities they're about as different as Gecko is from Blink, if not more so." > Not sure how familiar you are with the history of browser engines, but Blink and WebKit are definitely more similar than Gecko and Blink. I see we interpreted parent poster differently, he wasn't talking about the history of rendering engines, but rather compability with the various web specs. Since Chrome forked WebKit quite a long time ago now and Blink has been reworked quite a bit they have deviated from eachothers implementations. Since everyone is trying to follow an open spec it might be that in certain areas FF and Chrome implement more of the same API's than Safari, which doesn't have anything to do with codebase history. You might and probably will feel more comfortable in the WebKit codebase if you're a Blink developer or vice versa in comparision to Gecko, but that is if you're writing the engine itself and not pressing the pedals (targeting it).