A WEBTEST file contains a web test used by Visual Studio, a software development tool for Windows programs and web applications. It stores HTTP requests that have been recorded by the Web Test Recorder in a browser session or manually built by the Web Test Editor in Visual Studio. WEBTEST files are used by developers to test the performance of a website before it is published.

Web tests are used by Visual Studio to simulate how a user would interact with a website. These tests are performed on websites that under development, not websites that are live. WEBTEST files are typically created by Visual Studio but may also be created when exporting events from Fiddler, a web debugging proxy. You can open the WEBTEST file with the Web Test Editor tool, which is included with Visual Studio.