Download Fiddler from https://www.telerik.com/download/fiddler and install it.
Open Fiddler and go to Tools -> Options -> HTTPS tab. Enable Decrypt HTTPS traffic. You will be prompted to install the Fiddler Root certificate (this step requires elevated permission).
IE Compatibility test
Test how DOCTYPE and X-UA-Compatible affect the final document mode selection in IE browser
Enterprise Mode Lab
An online version of Enterprise Mode Site List manager, you can configure and serve your Enterprise Mode site list for testing purpose.
NTLM Authentication test
The page simply returns 401 Unauthorized to any anonymous request and accepts any NTLM authentication.
The Kerberos test page just returns "WWW-Authenticate: Negotiate" header if the request does not contain an "Authorization" header and displays the "Authorization" if the request header has it.
A simple application to test login/logout on Azure AD and Graph API. It is a multitenant application that supports accounts in any organization directory and personal Microsoft accounts.
The upload lab allows you to upload any JPG/PNG to the server, the server simply returns the file stream to the browser and browser then displays the image you uplaoded.