One tool I use quite often when developing products is ClipSpy.

It lets you see the contents of the Clipboard. A clipboard may have multiple formats stored. ClipSpy lets you analyze each format, see its data etc.

Yesterday, it helped me track the format in which Gmail accepts a file attachment via drag and drop (works only in Google Chrome browser). It uses the CFSTR_FILENAME clipboard format.

Earlier, when developing RecentX, it helped me track the clipboard formats that Windows Explorer uses when copying files.

Thanks.