Structured Headers Hard Mode is a Chrome extension that adds a layer of complexity by injecting 2 specific HTTP headers, sec-hardmode-list, and sec-hardmode-dict, to every web request. These headers utilize Structured Header syntax, aiming to test server compatibility with this syntax and potentially notify servers incapable of handling it.

This extension comes with a caution that it might disrupt normal functionality on certain websites. Users can easily toggle the extension on or off by clicking on its icon. For reporting any issues or broken sites due to the extension, users are encouraged to provide feedback on the GitHub page of the developer.