What works may be registered with electronic deposits?

“The following classes of works may be registered in eCO with electronic deposit copies:

• Unpublished works;
• Works published only electronically;
• special-deposit-requirements-section-of-circular-1-for-more-on-id-material);">Published works for which the deposit requirement is ID material (see the Special Deposit Requirements section of Circular 1 for more on ID material);
• Published works for which there are special agreements requiring the hard copy deposits to be sent separately to the Library of Congress.

— U.S. Copyright Office, eCO Online System

“All other classes of works may be registered via eCO (application and fee payment) but require hardcopies of the work(s) being registered.”
— U.S. Copyright Office, eCO Online System