Exclusively for you!! Trial version of Google Apps, Apply Coupon-CNHPGX6T6QRWGV!!

YSlow is a nice addon to determine page performance

Tools @Image courtesy of Thanamat/ FreeDigitalPhotos.net

YSlow is a nice addon to determine page performance

Welcome to CodeSpread!

YSLOW is one handier tool for a developer. It is used to analyze web pages and get it tested on the rules identified which are explained below. I like the name “YSlow”as it more or less poses a question “why slow?”. It is available as an add-on to most of the popular browsers like Firefox,Chrome,Safari etc. or can be downloaded from yslow.org.

Source: yslow.org

Yahoo!’s Exceptional Performance team has identified 34 rules that affect web page performance. YSlow’s web page analysis is based on the 23 of these 34 rules that are testable.

• Minimize HTTP Requests

• Use a Content Delivery Network.

• Avoid empty src or href.

• Add an Expires or a Cache-Control Header.

• Gzip Components.

• Put StyleSheets at the Top.

• Put Scripts at the Bottom.

• Avoid CSS Expressions.

• Make JavaScript and CSS External.

• Reduce DNS Lookups.

• Minify JavaScript and CSS.

• Avoid Redirects.

• Remove Duplicate Scripts.

• Configure ETags.

• Make AJAX Cacheable.

• Use GET for AJAX Requests.

• Reduce the Number of DOM Elements.

• No 404s.

• Reduce Cookie Size.

• Use Cookie-Free Domains for Components.

• Avoid Filters.

• Do Not Scale Images in HTML.

• Make favicon.ico Small and Cacheable.

I know we have been lazy in optimizing codespread.com but in some way, we are lucky that we can run yslow against it and catch many test results as failures to explain them here. Let’s run it on codespread.com.

First, we see the default screen of YSlow which gives us a slight idea about its operation.



Here, we can see a dropdown to select a ruleset of tests against which we would like run our website. We have 3 options available but we will select only the default option here to test the website against the latest version of ruleset available.



Overall, we have scored a D grade and a performance score of 70. Good news is, we have A grade in one or two instances like

• Avoid empty src or href.

• Put CSS at top.

Alert news is, F grade in instances like

• Make fewer HTTP requests.

• Use a CDN.

YSlow goes a step further and tells us the exact number of files and their types which are contributing to excess HTTP requests, plus what needs to be done to make it faster. That is the beauty of YSlow, It can make even an amateur understand the exact cause and also provides the suggestions for improvement. Here, we also see that not all rules are applicable in general case so we just need to look for the rules applicable to us and work on the suggestions.

YSlow is an awesome tool and also free. Just try it and share your experience.

Author: swatiS

Share This Post On


  1. nice superb explaination

    Post a Reply
  2. thanks for the tutorial
    I am having a problem.
    The feature “Create SQL server database” isn’t available , I can’t select it.
    Can you help, please ?

    Post a Reply

Submit a Comment

Your email address will not be published. Required fields are marked *

More from CodeSpread:

  • Do you know JsRender?Do you know JsRender?I am new to JsRender but still felt like discussing with my readers as may be one of our readers can provide more insights, after all, it’s a mutual learning that helps a community. What is JsRen...
  • Time Out: Not a Technical postTime Out: Not a Technical postTaking my time-out from technical world for once and sharing a regular joke in the form of  this comic with you. There is no harm in showing funny side also sometimes. wat say!!
  • Java script rendered content is not crawl able.Java script rendered content is not crawl able.There was a requirement to include 'ratings and reviews' plugin on the product pages of our website which is provided by a third party. We included a javascript library and some code as provided by...
  • Random Accessibility IssueRandom Accessibility IssueRecently, My friend asked me about a requirement regarding visibility of H1 and H2 tags. Although i faced the same situation some time back where i asked a lot many experienced persons mainly worki...
  • What is an API and What good is it?What is an API and What good is it?Did you anytime hear these questions? What is an API? Why it is required? How to make it? People have googled, few were satisfied and others came out perplexed. So why not we also try! W...
  • Styles of Source Code Comments in C#, SQL, XML, HTML, CSS, JavaScriptStyles of Source Code Comments in C#, SQL, XML, HTML, CSS, JavaScriptDevelopers take months to write beautiful pieces of code and reviewer gets only few hours or I say, minutes to provide suggestions and improvisations. Then it becomes a hard deal for a developer to...
  • 24/12/2013: 10 Best Practices of programming from CodeSpread(31-40)24/12/2013: 10 Best Practices of programming from CodeSpread(31-40)We love programming and having a knowledge of best practices always helps in writing beautiful code. We have shared first 20 random best practice in our previous articles 1-10, 11-20, 21-30. More b...
  • ASP.NET and Web Tools 2013.1 for Visual Studio 2012ASP.NET and Web Tools 2013.1 for Visual Studio 2012.NET Web Development and Tools group at Microsoft announces release of ASP.NET and Web Tools 2013.1 for Visual Studio 2012. Few of the features are: 1) Round tripping: With this update, developer...