I let the cat out of the bag about the forthcoming YSlow plugin for Firebug during my @media presentation (High Performance Web Sites) last month. But the wait is finally over and I’m happy to let you know that Steve Souders, Yahoo!’s Chief Performance Yahoo! (and the guy who’s data I used in my presentation), made the announcement during his session at OSCon yesterday.
YSlow has three main views: Performance, Stats, and Components. Performance view scores the page against each performance rule, generates an overall YSlow grade for the page, and lists specific recommendations for making the page faster. Stats view summarizes the total page weight, cookie size, and HTTP request count. Components view lists each component (image, stylesheet, script, Flash object, etc.) in the page along with HTTP information relevant to page load times. It also contains several tools including [Douglas Crockford's] JSLint.