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July 24, 2007
Yahoo! has released YSlow, their web performance tool, on YDN under an open source license. Steve Souders, Yahoo!'s Chief Performance Yahoo!, made the announcement during his session at OSCon.
YSlow measures web page performance based on the best practices evangelized by Yahoo!'s Exceptional Performance team. Since many of these best practices focus on the frontend, YSlow is integrated with Joe Hewitt's Firebug, the web development tool of choice for frontend developers.
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 JSLint. Try it out!
Posted at July 24, 2007 4:31 PM
Bad Package Error here when I try to install it.
Posted by: David Hall at July 24, 2007 8:08 PM
Yup, I'm also getting a bad package error downloading the extension. But I love the idea - can't wait to try it out, guys - cheers!
Posted by: Fred Oliveira at July 24, 2007 9:29 PM
The YDN "download now" fails for me same as other commenters but it installs correctly from the addons.mozilla.org "install now" button:
Posted by: Patrick Hunt at July 24, 2007 9:42 PM
The download URL changed when it was made public. Fixed now. Enjoy!
Posted by: Steve Souders at July 24, 2007 10:38 PM
This is a really great little tool. In a mater of an hour, I applied these theories to a project I am working on and came away with a much better performing application. I have to admit though, the fact that I'm not using a CDN and therefore score an F makes me sad... but I'm just not going to invest in that yet :)
~Jim
Posted by: Modeps at July 25, 2007 12:36 PM
Could we have a way of removing the "YSlow" status bar item?
Posted by: matte at July 25, 2007 1:38 PM
I'm getting an error saying "Not compatible with Firefox 2.0.0.5" in the Add-ons panel, and nothing shows up in Firebug. Is this a known issue or something I'm doing wrong?
Posted by: Alex at July 25, 2007 3:49 PM
This is great work guys...gonna put these guidelines into practice and see how much better our app can be.
Keep up the great work!
C
Posted by: Carlton Dickson at July 27, 2007 1:28 AM
We're getting great feedback on YSlow and building a list of fixes that will come out next week. A lot of people have commented about Rule 2 - Use a CDN. Make sure to read the FAQ link that's provided that describes how to add your own CDN to the YSlow preferences. That way you can get a realistic grade. We'll add a "turn off Rule 2" option next week. And an option to hide the statusbar info. Feel free to use the Feedback form to send in more suggestions.
Posted by: Steve Souders at July 28, 2007 10:42 PM
It chokes on images with "data:" as the src handler (src="data:hex-characters-here"), it breaks firebug.
For more reading on data urls see RFC2397
http://www.ietf.org/rfc/rfc2397.txt
Posted by: BW at August 9, 2007 4:07 AM
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