From the FAQ way down the bottom of the page: """ Will I get the same result as I would on a real device? Sizzy simulates the viewport and user agent of each

From the FAQ way down the bottom of the page: """ Will I get the same result as I would on a real device? Sizzy simulates the viewport and user agent of each device, so the results should be the same as what you would see on a real device. However, Sizzy cannot simulate different browser rendering engines, so there's a chance that there might be some minor differences when testing on a real device. """