ASP.NET 4.0 / AJAX Web Client Performance Improvements (Updated 1/14/10)

Lots of fantastic improvements are coming to ASP.NET 4 with regards to client web performance.  You can be sure that checks for these will be added to future neXpert versions! Permanent Redirection (ASP.NET 4) Using Response.Redirect will cause a HTTP 302 to be returned to the client thus creating an extra HTTP request every time. …


neXpert v1.2 Released

Only a minor update for neXpert which allows it to continue to work with the latest version of Fiddler. Fiddler version is required.  Currently this is the BETA release on Download here: Please provide any feedback you may have by emailing


neXpert at Velocity Conference This Week

The creator of neXpert, Eric Mattingly, will be at Velocity Conference this week presenting.  If you are attending, seek him out and share your experiences with the tool!  Also check out his session on Wednesday afternoon, Creating Instant Response Time Predictions with neXpert A video of the presentation will be posted as soon as it…


Capturing HTTP with Fiddler as a Reverse Proxy

My colleague on the ACE Performance Team, Vitaliy Konev, recently posted a blog post and video discussing how to set up Fiddler on a web server as a reverse proxy.  This is how you would capture HTTP traffic when you are not using a web browser client and you are also unable to configure the…


Creating Transactional Web Tests for Visual Studio with Fiddler / neXpert

One of the best features of Fiddler when performance testing is it’s ability to save a capture as a Visual Studio Web Test.  You can then use this web test to functional test or stick it in a load test to stress test your site. The latest version of Fiddler ( has an updated “Save…


Checking ASP.NET View State Size

There is a fantastic post over at Scott Hanselman’s Computer Zen where he discusses some of the performance improvements put into the newest version of MSDN. Specifically their performance team made the following changes: Moved CSS/JS around on different servers to better support HTTP pipelining (Current browsers will download 6 objects concurrently per server) Improved…


neXpert ExecAction Listeners

neXpert v1.1 introduces many different ExecAction listeners for both general Fiddler actions and some neXpert specific actions. Command Action Sample Usage       loadsaz filename Load a SAZ file into Fiddler. loadsaz c:\blog.saz savesaz filename Save a SAZ file of all captured traffic savesaz c:\blog.saz clearcookies Clear all WinINET cookies. clearcookies clearcache Clear the…


neXpert v1.1 Released!

A new version of neXpert (1.1) is now available on Microsoft Download Center. This release contains bug fixes, wording-changes as well as the addition of general and neXpert specific ExecAction listeners. The main fix is for a nasty localization issue identifiable by a number parsing exception.  (Thanks to all who reported it) Please check it…


neXpert mentioned in “Building High Performance Web Applications and Sites” at MIX09

John Hrvatin, a lead program manager on the Internet Explorer team, presented "Building High Performance Web Applications and Sites” at this years MIX.  In the talk he goes over many different aspects of web performance including: CSS performance Optimizing symbol resolution JavaScript coding inefficiencies HTTP performance Check out the video at


Setting Up Your Environment For Performance Testing

This rundown should help when using Fiddler for performance testing to perform captures correctly the first time.  If you have any feedback or additions to this list, please send them using the “Contact Us” link in the top left corner of the web page.  Thanks to Vitaliy Konev for some of the tips. Before any…