Mozilla's Mark Côté has reminded us that the arewefastyet page, which the browser maker launched prior to the introduction of Firefox 4, is still alive and is now tracking the progress of Mozilla IonMonkey JIT.
Though not an official statement made by Mozilla, Côté says that Firefox 18 (with IonMonkey) is now 16 percent faster than Chrome 21 in Mozilla's own Kraken benchmark, while it remains behind Chrome in V8 and behind Chrome in Sunspider. Mozilla's own
test page suggests that IonMonkey has improved from a time of 1991 ms with the first release of IonMonkey in Firefox in mid-August to currently 1933 ms. Chrome has improved from 2038 ms to 2019 ms in the same time frame.