Archive for the 'yslow' Category


Jun 27th, 2012

Say hello to the 3PO extension for YSlow. It checks your site for integration with popular 3rd parties, such as Facebook, Twitter widgets, Google Analytics and so on. 3PO (3rd party optimization) extension currently has 5 checks: two of them generic to all 3rd parties and three specific to Facebook plugins. I’m looking forward to […]


YSlow development: custom rulesets

Jun 20th, 2012

(This is part 3. See part one and part two.) There are two concepts to remember when working on your YSlow extensions and customizations: rules (or “recommendations” if you will, or “best practices” or simply “lint checks”), and rulesets which are lists of rules An example rule is “Reduce HTTP requests”. An example ruleset is […]


YSlow development: setup

Jun 19th, 2012

As promised, let’s setup for YSlow development using the easiest option – the bookmarklet version. The journey of conquering the world with your rules and extensions… starts with the first step. Checkout First you need to get teh codez. Go to the Github repository and click that big ol’ Fork button. Then checkout the repository […]


YSlow 2.0: the first sketches

Jun 11th, 2011

#4 This post is part of the Velocity countdown series. Stay tuned for the articles to come. I’m working on tomorrow’s kind of big thing, so will take it easy today, with a stroll down memory lane. I was clearing up my space at home few days ago and came across this oldish notepad. In […]


YSlow/Chrome hacking

Mar 24th, 2011

If you haven’t seen it yet, YSlow for Chrome hit the streets couple of weeks ago. (And Google’s own PageSpeed did too yesterday. (And there’s now DynaTrace for Firefox. (And WebPageTest for Chrome. (What a month for x-browsering (word?) the performance tools! (And the month’s not even over yet))))) BTW, I closed all the parentheses […]


Web Testing Framework

Jun 20th, 2010

There’s a new version and now hosted on AMO ( Get the new version there and it will take care of auto-updates in the future. WFT Web Testing Framework (WTF) is an extension to YSlow that tests for the following shady web dev practices: Use of <blink> Use of <marquee> Use of <font> Missing doctype […]


Performance tools

Dec 2nd, 2009

2010 update: Lo, the Web Performance Advent Calendar hath moved Dec 2 This is the second in the series of performance articles as part of my 2009 performance advent calendar experiment. Stay tuned for the next articles. While theoretically you can speed up your site by just blindly following advice from this blog and other […]


“Don’t make me wait” – slides from my eBay tech talk

Aug 19th, 2009

Here are the slides from a tech talk I gave at eBay last week, I called it “Don’t make me wait! or how to build high-performance web apps”, inspired by, you guessed it, the excellent book “Don’t make me think” by Steve Krug. There’s some intimate details on YSlow’s scoring algo towards the end and […]


My online footprint lately

Jul 23rd, 2008

This is a sort of a catch-up post for listing what I’ve been up to lately. YUI Blog just published my first article, I’m so proud. It’s about loading JavaScript in non-blocking fashion, because JavaScripts, they, you know, like, block downloads. Luckily, there’s an easy fix – DOM includes, which I’ve previously discussed, discussed and […]


Happy Download Day

Jun 17th, 2008

Today is the Download Day for Firefox, which means the new release FF3 is out now. Go ahead, download and help set a Guiness record for the most software downloads in a day. Also, last night we released a new YSlow version that works with FF3 and the latest Firebug 1.2 beta (and also FF2, […]


20 new performance best practices

Mar 18th, 2008

The slides from my PHP Quebec presentation in Montreal are up on slideshare. Roughly the content is divided into: a quick review/update to Yahoo’s existing 14 best practices for improving performance, and a discussion of the 20 new ones Enjoy responsibly and don’t hesitate to send back questions and comments. And how about this slide […]



Dec 5th, 2007

One of the hidden perks about working at Yahoo! is that you get to interact with a lot of smart people, and even some celebrities in the web dev profession. Rasmus Lerdorf, Douglas Crockford, YUI guys, the list is way too long… Those couple of weeks I had the pleasure of working closely with Steve […]


YSlow performance extension for Firebug

Jul 25th, 2007

Steve Souders, performance architect at Yahoo, announced today the public release of YSlow. What’s YSlow? It’s an extension to Firebug (yes, correct, Firebug, not Firefox) that helps with performance optimization efforts. It scores your page on the scale A to F, based on compliance with Yahoo’s performance rules. It’s a tool that has been used […]