Fiddler Everywhere provides a powerful debugging technique for editing the captured traffic.
Instead of testing your API or a website through the UI and making multiple clicks, you can reload the desired session in the Composer tab, make edits to the desired values, and re-execute the request.
To load and modify a session through the Composer:
Set Live Traffic to Capturing and make the request. As a result, the session is captured and displayed in the Live Traffic list.
Select the desired session and right-click to open the context menu. From the context menu, select Edit in Composer. Alternatively, select the session and use the keyboard shortcut by pressing the E key.
The session opens in a new Composer window and then you can change the desired values. For example, change the data payload, modify the headers, test the authentication, and so on.
To modify a header, select it and change the needed key-value pair. You can add a new header by using the top key-value row. By default, the top key-value row is empty and can receive new values. Once you have modified or added a new header, click the confirmation button (a tick) to the right to apply the changes.
This approach enables you to modify an existing request in the same way your application does it. In the Live Traffic list, you can find the newly executed request and the response from the server.