No, we are talking about the architecture of the browsers in areas where there is significant impact (ie. UI Responsiveness), this has nothing to do with extens

No, we are talking about the architecture of the browsers in areas where there is significant impact (ie. UI Responsiveness), this has nothing to do with extensions. In Chrome when you load a JS-intensive website (ex. Facebook) you can switch to a different tab while the website finishes doing that JS-intensive task (ex. loading), but in Firefox the opposite happens, the entire browser freezes so you are forced to wait until the browser becomes responsive again. We are talking in the order of magnitude of milliseconds, but unfortunately it is enough to be perceptible (and annoying). Fortunately for FF, e10s[1] is almost baked, it still doesn't feel as responsive as Chrome BUT it feels significantly better so you can easily neglect the difference until it matures or something better (Servo[2]) gets baked. [1] https://wiki.mozilla.org/Electrolysis https://wiki.mozilla.org/Electrolysis [2] https://servo.org/ https://servo.org/