Why is Selenium InternetExplorerDriver Webdriver very slow in debug mode (visual studio 2010 and IE9)

For me, the fix was to switch to the 32 bit version of InternetExplorerDriver.exe from https://code.google.com/p/selenium/downloads/list

Seemingly named IEDriverServer nowadays, but works if you just rename it to InternetExplorerDriver.exe.

check 'prefer 32 bit' is not checked in your build properties. If it is and you are using the 64 bit IE driver it will run like an asthmatic snail.

Using the C#, NUnit, C# webdriver client and IEDriverServer, I originally had the problem with slow input (e.g., sending keys to an input box would take about 5 seconds between keys, or clicking on a button same kind of delay).

Then, after reading this thread, I switched to the 32-bit IEDriverServer, and that seemed to solve the problem.

But today I was experimenting with the InternetExplorerOptions object in order to set some options on IE according to this documentation:

https://code.google.com/p/selenium/wiki/InternetExplorerDriver

Per the documentation, I created the registry value HKCU\Software\Microsoft\Internet Explorer\Main\TabProcGrowth with a value of 0 in order to use ForceCreateProcessApi = true and BrowserCommandLineArguments = "-private."

After doing this, I noticed that the slow-input problem was back. I had made several changes to my code, but after rolling all of them back, the problem still persisted. When I removed the aforementioned registry key, however, the input was back to full speed (no delay).