YSlow 0.9 Release – Better Support for Web 2.0

We're excited to announce the release of YSlow 0.9, Yahoo!'s web page performance analysis tool. There are two big features in this release. By integrating more tightly with Firebug's Net Panel, YSlow now finds non-DOM components such as Ajax requests and image beacons. And YSlow now crawls frames and iframes and analyzes those resources as well. There are several other new features and bug fixes described in the release notes including highlighting 404s, better detection of CSS expressions and JavaScript minification, and searching within the YSlow panel.

These features make YSlow stronger at identifying performance improvements for Web 2.0 applications. It's great that YSlow does even better performance analysis of pages, but be forewarned that your previous YSlow scores will drop if these new-found components exhibit bad performance characteristics. As mentioned in Rule 14 - Make Ajax Cacheable, some of the performance improvements that are readily applied to static content (far future Expires header, gzip compression, minification) can also be applied to Ajax responses. Whether it's Web 1.0 or Web 2.0, YSlow 0.9 helps you figure out what to fix to make your pages faster for your users.

Steve Souders
Stoyan Stefanov