Web Performance Measurement with Fiddler

Getting Started

Learn about Performance Tuning with Fiddler.  Also, check out my talk at the Velocity Performance Conference and the associated slide deck.

Check out the Fiddler Tutorial Videos.  Video #3 covers Performance Measurement.

Want Fiddler to add latency to all requests?  Check out the Latency Extension for a simple way to do this.

Expert Analysis

neXpert is an add-on to Fiddler which aids in performance testing web applications. Learn more...

Deep-Dive

Advanced readers may want to take a deep-dive into the nitty-gritty of performance measurement techniques and the Observer Effect.  Fiddler is not designed for low-level TCP/IP measurement; for that, you want to use a tool like NetMon + VRTA. Of course, it's important to keep in mind that the vast majority of site performance problems have nothing to do with TCP/IP-level details. Any low-level measurements you take are likely to be specific to your environment, and cannot necessarily be generalized to other environments worldwide, with different proxy configurations, etc.

Tips & References for Optimizing Performance

• Don't use "pre-check=0, post-check=0" in your Cache-Control directives in an attempt to prevent caching.  That is not what they're meant for, so sending them is wasteful.  Use the proper "no-cache" directive instead. 
• Avoid using the Vary response header unless you absolutely must.  Internet Explorer's support for Vary is limited.
• Steve Souders' Rules for High Performance Websites
• High Performance DHTML
• High Performance HTML
• Javascript Performance article #1
• Javascript Performance article #2
• Javascript Performance article #3
• Javascript Memory Leak Detector
• Google's "Make the Web Faster" pages