How to Measure Website Performance with Three Free Tools

Everyone prefers websites that download quickly. As a result, we’re likely to move on to other, competing websites if a website downloads slowly. For example, Nielsen’s rule of thumb is that websites should download in ten seconds or less. To reflect our desire for faster websites, and to improve our overall web user experience, Google now includes download speed in its calculation of a website’s placement in its search results; Google rewards faster websites with a higher placement. This post describes three free tools for measuring the performance of your website.

Google Page Speed

The first free performance-measuring tool is Google’s own Page Speed. Simply enter the URL of your website and click the Analyse Performance button. Page Speed rates websites between zero to 100; the faster the website, the higher the score. For example, the following screenshot shows that Usability, etc. gets a respectable 87 out of 100.

Google Page Speed results for Usability, etc.

Page Speed also makes suggestions for improving the score, which it ranks as high, medium and low priority. This screenshot shows the suggestions for Usability, etc.

Google Page Speed suggestions for Usability, etc.

Clicking on a suggestion presents a detailed list of resource files ripe for optimization. Resources include JavaScript files, CSS files and image files. For example, this next screenshot shows the list of Usability, etc. resource files that don’t leverage browser caching.

Detailed Google Page Speed suggestions for Usability, etc.

Always implement higher-priority suggestions before tackling lower-priority suggestions; the higher the priority of the suggestion, the greater the performance improvement after implementing the suggestion.

Google PageSpeed tells you which resource files need attention, but it doesn’t tell you how long your website takes to load, or how long each resource file takes to load. To get more detailed information, use Pingdom.


The second free performance-measuring tool is Pingdom. Pingdom provides a detailed, visual breakdown of how long your website and its resource files take to download. To get the breakdown for your website, enter its URL in the box and click the Test Now button. The following screenshot shows the visual breakdown of Usability, etc.

Pingdom results for Usability, etc.

Pingdom uses the following colour key:

  • Yellow—the time elapsed between requesting the resource file and making the connection with the web server.
  • Green—the time elapsed between requesting the first byte of the resource file and receiving the first byte.
  • Blue—the time elapsed between receiving the first byte of the resource file and receiving the last byte; that is, how long the resource took to download.

Pingdom’s strength is its visual breakdown; web developers can see immediately which resource files reduce website performance. Pingdom doesn’t provide a performance score or detailed suggestions for improvement like Google Page Speed, but it does provide a useful summary below the detailed, visual breakdown. Here’s the Pingdom summary for Usability, etc.

Yahoo! YSlow

The final free performance-measuring tool I describe in this post is the Yahoo! YSlow add-on for the Firefox web browser. YSlow helps web developers implement the Yahoo! best-practices for high-performance websites. YSlow requires the Firebug add-on for web developers, which you need to install before installing YSlow.

Like Google Page Speed, YSlow rates website performance. YSlow rates websites with a grade from F (the lowest) to A (the highest). Also like Page Speed, YSlow provides detailed suggestions for enhancing performance. YSlow helpfully grades each category of suggestions so that web developers can see improvements after implementing the suggestions in a category. The following screenshot shows the YSlow results for Usability, etc.

YSlow results for Usability, etc. using the Small Site or Blog Ruleset

YSlow can analyse websites with several rulesets, each geared toward a different type of website. The above screenshot shows that YSlow gave Usability, etc. a grade B for a score of 87 out of 100 using the Small Site or Blog ruleset. The YSlow(V2) ruleset provides a more detailed analysis, but it also provides more categories of suggestions for improvement. For example, this final screenshot shows that YSlow gave Usability, etc. a grade C for a score of 74 out of 100 using the stricter YSlow(V2) ruleset.

YSlow results for Usability, etc. using the V2 Ruleset


The following table summarises the characteristics of the three free website performance-measuring tools described in this post.

Performance Tool Score or Grade Detailed Suggestions Visual Presentation
Google Page Speed Yes Yes No
Pingdom No No Yes
Yahoo! YSlow Yes Yes No

Each tool has its advantages, but no single tool has the advantages of all three tools. Therefore, the best approach is to use all three tools to measuring your website’s performance. In addition, implementing the Google Page Speed and Yahoo! YSlow suggestions for your website will improve both its Page Speed score and its YSlow grade.

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