The United States Patent and Trademark Office’s patent information system which superseded PAIR it can display most public information relating to patents filed after about 2001/2 usually including the full file wrapper of most patents PAIR had two sides.
Patent Center allows ordinary members of the public to obtain information if they have a patent number or a patent application number; Private information requires registration and the use of a password and allows a patent holder and its agents to view that status of pending unpublished patent applications and other data such as the payment of maintenance fees.
The European Patent Office maintains an analogous system, the European Patent Register.