Rediscovering your site with YSlow

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Since it’s crucial to have a responsive site let alone online store you’ll definitely want to do anything humanly possible to make that store run fast. Here’s one way of doing it.

Why is my site slow?

Well, I don’t know but if you have Firefox installed on your computer you can add one more valuable add-on: Y-slow and find out for yourself 🙂


Introduction to YSlow from their site:

YSlow analyzes web page performance by examining all the components on the page, including components dynamically created by using JavaScript. It measures the page’s performance and offers suggestions for improving it.

The new YSlow will not only measure, suggest it will also do the legwork for you by resizing images if you choose using the famous tool.

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As you can see from the screenshot will even neatly organize the archive of the images for you to download.

As far as how does the YSlow works Yahoo team states that they have identified 34 rules that affect web page performance and Yslow test 22 of those. Some of them are well known as the size of the files or that “never do it please” HTML resizing of the images and so on but what about other rules you should follow to optimize site’s performance?

Here is the list:

  1. Minimize HTTP Requests
  2. Use a Content Delivery Network
  3. Add an Expires or a Cache-Control Header
  4. Gzip Components
  5. Put StyleSheets at the Top
  6. Put Scripts at the Bottom
  7. Avoid CSS Expressions
  8. Make JavaScript and CSS External
  9. Reduce DNS Lookups
  10. Minify JavaScript and CSS
  11. Avoid Redirects
  12. Remove Duplicate Scripts
  13. Configure ETags
  14. Make AJAX Cacheable
  15. Use GET for AJAX Requests
  16. Reduce the Number of DOM Elements
  17. No 404s
  18. Reduce Cookie Size
  19. Use Cookie-Free Domains for Components
  20. Avoid Filters
  21. Do Not Scale Images in HTML
  22. Make favicon.ico Small and Cacheable

It comes with three already defined rulesets but you can make your own rulesets and/or edit the existing ones.

The actual window of YSlow offers you 4 main tabs that cover site’s grade, list of site’s components, statistics and tools like JSlint or as mentioned at the beginning of the post.

Head over to YSlow page for more detailed and elaborate content on how to install and use this tool.


  1. Thanks for reminding me to check my site with YSlow. I’ve been having little “slowage” lately after relaunching my site. I’m getting As and Bs on most except Server tab. Full of Fs. It’s recommending me to utilize Content Delivery Networks (CDN)

    I would love to read an article about Magento and use of CDNs if you have experience in this field. Benefits; providers; cost; setup; etc.

    Thanks for providing us with great info on Magento as usual.

    – monocat

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