VIRTUALIZING EXTENSION CODE IN AN APPLICATION

Techniques are described herein that are capable of virtualizing extension code (e.g., third-party extension code) in an application (e.g., a web application in a browser). A portal of an application that is associated with an extension is loaded. For instance, the portal may have extensibility points to enhance its functionality in a secure manner. The extension includes metadata and implementation code. The metadata is loaded. In response to the portal being loaded, the implementation code may not be loaded until a user interaction occurs.