DareBoost!

Pingdom web site monitoring and other infrastructure for you and instantly let you know when anything goes wrong. Measure uptime, downtime, and the performance of your website as experienced by visitors.

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.

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.

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

Run a free website speed test from multiple locations around the globe using real browsers (Firefox, IE, Chrome, Android and iOS) and at real consumer connection speeds. You can run simple tests or perform advanced testing including multi-step transactions, video capture, content blocking and much more. Your results will provide rich diagnostic information including resource loading waterfall charts, Page Speed optimization checks and suggestions for improvements.

Comprehensive website and web application monitoring:* simulate a real browser (Firefox) to check performance* services monitoring (FTP(S), DNS, PING, TCP, SSL, SMTP, POP)* user experience monitoring (browser load time per user-agent, response time in various platforms* response time and throughput of each web transaction with graphical representation for quick performance insight* performance stats by ISP* application performance monitoring (monitor Java, .NET and Ruby on Rails web transactions and drill down to offending code and pinpoint root cause of issues from the cloud)* cloud monitoring (Amazon EC2, RDS instances and S3 Bucket)* VMware Monitoring* server Monitoring (Linux, Windows)* On-Premise Poller to monitor intranets* monitor from 3G/4G carriers* DNS server monitoring* SSL certificate expiration monitoring* notifications via SMS, Email, Push Notifications, Twitter and RSS Feeds* mail server, Exchange, FTP monitoring* API, user management* Root Cause Analysis - a comprehensive report based on trace route, ping output, DNS reports and web page screenshots that gives you a conclusion on what caused the issue »

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.

Website performance monitoring displaying the load times for various components of the site. Plans start at $23/mo.

Free & Simple website monitoring

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

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

365andUP's WebAnalytics is a free tool that analyzes your website's performance loading it in real browser, record it and show actionable insights which will help you optimize and be a search engine friendly website.