Editors' Note: The Download Now link will prompt a local download of the Firefox extension. To install the extension directly, open the file using your Firefox browser.
YSlow analyzes Web pages and tells you why they're slow based on Yahoo's rules for high performance Web sites. YSlow gives you performance report card, HTTP or HTML summary, list of components in the page, and tools including JSLint.
What's new in this version:
Version 3.1.4 has fixed Firebug init issue.