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Speed up your web pages with YSlow

YSlow analyzes web pages and tells you why they're slow based on the rules for high performance web sites. YSlow is a Firefox add-on integrated with the popular Firebug web development tool. YSlow gives you:

Install Firebug first!

• Performance report card
• HTTP/HTML summary
• List of components in the page
• Tools including JSLint

Podcast, Screencast

Take a look at the YSlow Podcast and Screencast.

Performance View

YSlow analyzes any web page and generates a grade for each rule and an overall grade. If a page can be improved, YSlow lists the specific changes to be made.

Stats View

YSlow calculates the total size of the web page for both empty cache and primed cache scenarios, as well as information about cookies.

Components View

YSlow lists all the components in the page including their type, URL, Expires date, gzip status, load time, size, and ETag. You can also view the HTTP response headers for any component.

YSlow Docs & Help

Learn more about YSlow's features and how to use it in detail from our YSlow Docs & Help.

Developer Support & Community

YSlow development is discussed on the Exceptional Performance Group. Use this group if you have questions, issues, or need technical support.

Feedback?

The YSlow team is happy to hear your feedback. Write to us.

Licensing

YSlow is open source licensed. Please refer to the YSlow Licensing FAQ.