Generated ID is just a random number from 0 to 3 999 999.
There's about a fifty-fifty chance that you'll get a post that is both valid, and not somehow concealed by privacy settings.
Do not share or interact with posts that are clearly private or untagged, regardless of privacy status. I will take down this tool if such activity is reported.
Use the tag 'random post generator' if you reblog these posts, so people can blacklist.