The present invention extends to methods, systems, and computer program products for capturing diagnostics for Web browser applications. Embodiments of the present invention can capture errors in client-side code for a Web application and automatically report them a Web Service. Diagnostics code can be automatically injected into client code to capture client-side diagnostic information, including but not limited to errors in Web application code (script code, managed code, etc) that runs in a Web browser. The client-side diagnostic information can be automatically forwarded to a Web service under the control of the Web application. The Web application operator can use this information to improve the quality and hence customer satisfaction of their Web application.