Private Browsing automatically erases your browsing information, such as passwords, cookies and history, leaving no trace after you end the session.

Please Install Advanced Features to capture pages in the Private Browsing mode.

FireShot works for any webpage, but with some exceptions, which are regulated by the browser's security policy.

Fortunately, only a few page types are protected from script execution: blank, extension, and startup pages.

You can try out any other web page, for example this page.

FireShot needs your approval to capture this resource. Please go to the options and check the Allow access for file URLs box.

HINT: see this short manual how to enable this option.