The methods track abnormal events on mobile client devices, such as web application crashes, and use that information to associate the abnormal events with device characteristics. A first method executes on mobile client devices. When a web application starts, the method looks for a crash indicator cookie in persistent memory. If the cookie does not exist, the method creates and stores it. If the cookie already exists, the method collects information about the client device, such as device type, browser type, and operating system, and sends the information to a web server. The web application deletes the cookie when the application terminates normally. A second method executes on a web server. This method receives information from client devices relating to abnormal events for web applications. The information includes device characteristics of each client device. This method stores the information and associates a pattern of abnormal events with device characteristics.