If you want to perform web testing on multiple browsers and operating systems, it can be quite complicated to maintain machines for each of the target environments. BrowserStack provides “remote web browsers as a service”, making it easy to do this sort of matrix testing without having to maintain the multiple browser installations yourself. Specflow provides easy integration with BrowserStack.
To help you use Browserstack and Selenium together with SpecFlow we have put together this plugin. Check it out for more details.