Who can register online?

“Anyone can use eCO to register basic claims to copyright, even those who intend to submit a hard copy(ies) of the work(s) being registered. Basic claims include literary works, visual arts works, performing arts works, sound recordings,motion pictures, and single serial issues. At this time, the following types of registration are not available in eCO: renewals, corrections, mask works, vessel hulls, groups of serial issues, groups of newspaper/newsletter issues, groups of database updates, and groups of contributions to periodicals.For information about registering these types, see the Copyright Office website.”
— U.S. Copyright Office, eCO Online System