Since version 2.0, YSlow is no longer just a tool, it's a platform. You can create your own rules (performance or otherwise), combine them into rulesets, tweak scores to your liking and so on.
Once Marcel took over and did version 3.0. YSlow can now run in many many environments: as a Firebug extension (like version 1.0 did), as a Firefox extension, Chrome extension, command-line and so on... including running as a bookmarklet in any browser (including mobile browsers). Funny aside is that YSlow version 0.XYZ was originally just a bookmarklet. Now it's a bookmarklet among everything else.
We'll be using the bookmarklet version for development.
What's even lovelier is that YSlow is open source now on Github.
I wish I could tell you more, but it's father's day and the backyard BBQ party (including a rare live appearance from Anaconda Limousine) starts in an hour. And something tells me I won't feel very bloggy after the party. So YSlow would have to wait.
If you cannot wait though here are some pointers:
- Github repo - where the wild codez live
- Docs and stuff
- YSlow 2.0 architecture - to warm up with the API (+sketches)
- WTF - an example extension
- Follow Marcel "the YSlow guy" Duran
So welcome to the exciting world of YSlow development, it's fun and games and new rules and new integrations and pure webperf joy!