Best FireFox Addons to Analyze Page Load Time

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Keeping track of your site page load time is essential because it effects both the user experience and the crawl rate. This post lists 3 most useful FireFox addons that will help you analyze web page load time as you browse:


YSlow is the official Yahoo! addon that integrates with Firebug. YSlow analyzes web pages and suggests ways to improve their performance based on a set of rules for high performance web pages. When installed, it adds a tiny icon to FireFox status bar which shows the current page load time:


Google’s Page Speed

Page Speed is a Firefox/Firebug add-on that performs several tests on a site’s web server configuration and front-end code. These tests are based on a set of best practices known to enhance web page performance.

Webmasters who run Page Speed on their pages get a set of scores for each page, as well as helpful suggestions on how to improve its performance.

It adds an extra tab to Firebug that allows to analyze current page speed:

Google page speed

LORI (Life-of-Request Info)

LORI (Life-of-Request Info) is an advanced FireFox addon that adds a status bar at the bottom right corner of Firefox and displaying:

  • TTFB: how long it took to see the first byte from remote server (from click to first byte received).
  • TTC: how long it took to display the page (from click to complete drawing of the page)
  • Page size (number of bytes used to display the page): this value includes both bytes fetched from network and bytes fetched from the browser’s cache.
  • Number of requests: number of requests used to fetch the page’s content (images, style-sheet, javascript ….). Again, this value include both network requests and cache requests.

Note: it looks like it is not compatible with current FireFox version but it is a classic tool for page load time analysis so I couldn’t help mentioning it. Please comment here once the addon is updated.

Ann Smarty

Ann Smarty

Brand amd Community Manager at Internet Marketing Ninjas
Ann Smarty is the blogger and community manager at Internet Marketing Ninjas. Ann's expertise in blogging and tools serve as a base for her writing,... Read Full Bio
Ann Smarty
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  • QoSyS

    thnx, nice post.
    Russian translation ->

  • Luke

    A good round up. I’ve tried both Yslow and Google Page Speed and prefer the later – probably because I’m a Firbug fan though.

  • Sankar

    Haven’t heard about LORI (Life-of-Request Info) till now. Needs to check it out.


  • Offerte ADSL

    Hello, i have just tried YSlow: it works great. Thank you.

  • MaxASPSteve

    Only two complaints about LORI (Life-of-Request Info), not compatible with new versions of FireFox, and TTFB is a great metric, but TTLB is also necessary when evaluating site/webserver performance

  • mbeacho

    I have FF 3.5.3 and I just downloaded the LORI addon. It seems to be working with no issues now.

  • frank d

    Thanks for this post. Found it to research a better analysis tool.

    Do you also get such vastly inconsistent results between the different tools? To the point one might need to run maybe three or four at the same time?

    Because I’m now trying extended statusbar and LORI at the same time, and I can’t get them to agree when visiting sites like cnn, macworld, … It is hit or miss which one will be correct when it comes to load or completion.

    For this page Extended says 51KB , while LORI says 2.31KB? Both .2 sec completion.