WebPagetest!

GTmetrix is a free tool that analyzes your page's speed performance. Using Page Speed and YSlow, GTmetrix generates scores for your pages and offers actionable recommendations on how to fix them.

Yellow Lab Tools checks a website for both it's performance and the quality of the HTML, CSS and JavaScript code.

PageSpeed is addon for Firebug (debugger addon for Mozilla Firefox ) for analyzing of page loading process and suggesting to webmaster how speed up page loading. Javascript obfuscating, image resizing, CSS merging and vise versa.

Without any installation, we continuously analyze your web pages to detect quality and loading times issues. At any time, you can see the evolution of the major performance indicators of your pages on your dashboard, or in your weekly emailed reports.

Lighthouse is an open-source, automated tool for improving the quality of web pages. You can run it against any web page, public or requiring authentication.

YSlow analyzes web pages and suggests ways to improve their performance based on a set of rules for high performance web pages. YSlow is a Firefox add-on integrated with the Firebug web development tool. YSlow grades web page based on one of three predefined ruleset or a user-defined ruleset. It offers suggestions for improving the pages performance, summarizes the pages components, displays statistics about the page, and provides tools for performance analysis, including Smush.it™ and JSLint.

Site Toolbox for the website owner, web engineer, SEO analyst, web developer, webmaster and everyone.

WDT - Web Developer Tools is a suite of useful tools for web developers

Website speed test, DNS lookup service incl EDNS client subnet, fast geolocation for IP or hostname, HTTP response headers, FREAK attack tester and more.

Get free notifications if your page speed changes, fast and easy.

StatusCake Tools allows you to check the speed and load time of your website. Simply enter the website URL and check one of the locations from around the world you want the website checked from.

MachMetrics continually monitors the speed of your website. So you know exactly how your pages are performing throughout the day, around the world, and on various devices

neXpert is an add-on to Fiddler Web Debugger which aids in performance testing web applications. neXpert was created to reduce the time it takes to look for performance issues with Fiddler and to create a deliverable that can be used to educate development teams.