The purpose of a .asax file in web development is to handle and manage application-level events and settings in an ASP.NET web application. It is an optional file that is automatically generated when creating a new ASP.NET application.Some common uses of the .asax file include:Global Application Events: The .asax file allows developers to handle events that occur at the application level, such as application start, end, session start, session end, error handling, etc. This enables developers to write code that runs when these events occur, providing a way to initialize resources, manage sessions, log errors, etc.Application-Level Settings: The .asax file can also be used to define and configure application-level settings that are accessible throughout the application. These settings can be used to store and retrieve information that is required by multiple pages or components within the application.URL Routing: With the introduction of ASP.NET MVC, the .asax file can be used to configure URL routing rules. Routing allows developers to define custom URLs for different pages or actions within an application, providing more user-friendly and search engine optimized URLs.Overall, the .asax file acts as a central location to define application-level events, settings, and routing rules, making it an essential part of ASP.NET web development.