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:
- Performance report card
- HTTP/HTML summary
- List of components in the page
- Tools including JSLint
Install Firebug first!
Visit Yahoo! Exceptional Performance on YDN.
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.
YSlow calculates the total size of the web page for both empty cache and primed cache scenarios, as well as information about cookies.
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.