Measure web page performance with YSlow.

28 בינואר 2009

3 תגובות

My colleague Ran Wahle posted a great article about Firebug add-on for Firefox that provides debugging abilities for the browser. In this post I will introduce an add-on for Firebug called YSlow released by "Yahoo! Developer Network". It’s used to analyze web page’s performance and supplies detailed report on HTML page structure along with number of recommendations on how to improve performance of that page.

Analyze web page performance

Usage of YSlow is very intuitive – after installing, click on it’s icon in status bar starts page analysis. In addition to this manual activation YSlow has a “Autorun” mode, meaning that it will run continuously on each page you get into.


YSlow analyzes a web page by 13 categories and gives a "Performance grade" in each category, in addition there is common performance score based on "weight" of each of those categories, displayed on the top of the window.


Click on arrow beside of any category will display list of all related elements:


Direct click on category will open Yahoo's web site with complete description of the problem and recommendation for handling of a problem on several web platforms. Total performance grade that is under "D" – means your web site needs some improvements…

Stats view

Click on menu "Stats" menu item displays a pie diagram with analysis of page content(HTTP requests, total size of transferred data, cookies etc.) in two modes:

  1. Empty cache – shows page’s content analysis on first time page load with no cached items.
  2. Primed cache – displays a content analysis of the page after it was cached on first load.



Components view

Click on "Components" menu item provides complete information about all elements that are being downloaded on selected web page. The displayed data helps to identify components that without expiration date (which i will elaborate in one of my upcoming posts), or not compressed with Gzip data compression, long load time etc.


In Conclusion

YSlow is simple to use and free of charge tool that helps to identify performance problem of selected web page, in some cases it can identify issues on a web server level, and suggests some ways to resolve found issues. In my upcoming posts I will describe how to fix some of those problems in ASP.NET applications and IIS servers.

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3 תגובות

  1. alikl28 בינואר 2009 ב 10:22

    Great distillation – very prescriptive and practical
    thanks for sharing!

  2. Maor David-Pur28 בינואר 2009 ב 16:44

    great post!
    thanks for sharing.

  3. FunnyDevil28 בינואר 2010 ב 5:15

    It is very interesting for me to read this article. Thanx for it. I like such themes and anything connected to this matter. I definitely want to read a bit more soon.