Web page analysis
PageSpeed – Open source Firefox/Firebug Add-on that evaluates the performance of web pages and gives suggestions for improvement.
Speed Tracer – Google Chrome extension that helps you debug performance problems with AJAX applications.
WebP – Reduce image file sizes and download times.
PageSpeed ServiceNew! – PageSpeed Service is an online service to automatically speed up loading of your web pages. PageSpeed Service fetches content from your servers, rewrites your pages by applying web performance best practices and serves them to end users via Google’s servers across the globe.
From other developers
Cuzillion – Tool for quickly constructing web pages to see how components interact and how behavior differs across browsers, sometimes in unexpected ways. Also lets you share sample pages with others.
Hammerhead – Firebug Add-on for measuring the load time of web pages.
OOCSS – Development environment and framework for creating fast, reusable CSS objects and modules.
httperf – Tool for generating HTTP workloads and measuring web server performance, and constructing micro- and macro-level benchmarks.
mon.itor.us – Provides a personalized Ajax dashboard interface, checks server performance and availability, generates uptime reports, tracks visitors, checks CPU, memory and other systems resources, and alerts when it detects abnormalities.
Pylot – Open source tool for testing the performance and scalability of web services. It runs HTTP load tests, verifies server responses, and produces reports with metrics.
Wbox – Performs various tests, including page load benchmarking, web server and web application stress testing, and verifies correct configuration of virtual domains configuration, redirects, and HTTP compression.
Xdebug – Extension for PHP that provides profiling and code coverage analysis, as well as debugging information including stack and function traces, and memory allocation.
XHProf by Facebook – Instrumentation-based hierarchical profiler for PHP.
CSS Sprite Generator – Generates a CSS sprite out of a number of images.
Smush It – Online tool that allows you to upload images for lossless compression and optimization. Provides a report of bytes saved and downloads a zip file containing the optimized versions of the files.
SpriteMe! – Tool that determines background images to sprite, groups and sprites them, and generates resultant modified CSS.
Fiddler 2 – Web debugging proxy which logs all HTTP/S traffic between your computer and the Internet. Inspect HTTP/S traffic, set breakpoints, and “fiddle” with incoming or outgoing data.
HttpWatch – HTTP viewer and debugger integrated with IE and Firefox to provide HTTP/S monitoring without leaving the browser window.
Web page analysis
BrowserMob – Tool for website performance monitoring and alerting.
IBM Page Detailer – Graphical tool that assesses web page performance and provides details include the timing, size, and identity of each item in a page.
Microsoft VRTA – Tool that visualizes web page download, identifies areas for performance improvements, and recommends solutions.
MySpace Performance Tracker – Internet Explorer browser plugin that helps improve web page performance by capturing and measuring possible bottlenecks.
WebPagetest – Tool that provides a waterfall of your page load performance as well as a comparison against an optimization checklist.
Show Slow – Open source tool that helps monitor website performance metrics over time. Captures the results of YSlow, PageSpeed and dynaTrace AJAX Edition rankings and graphs them, to help you understand how various changes to your site affect its performance.
Yahoo! YSlow – Firefox/Firebug Add-on that analyzes web pages and suggests ways to improve their performance, based on a set of rules for high performance web pages.