Various definitions exist for the term "public domain" throughout the world. In the U.S., for example, the general rule is that pre-1923 published works are public domain, unpublished works are under federal copyright for at least the life of the author plus 70 years. In Germany and Austria, the "Gemeinfreiheit" term generally applies to the lifting of copyright from works (artwork and text) 70 years after the death of the author. Public domain and its equivalent German term are, however, subtly different concepts, as is the case in other international contexts.

The Creative Commons project has now reacted to the various loopholes in the "public domain" definition with a new proposal: with CC0 license you waive all copyright and related rights to a work, including databases, in a "no rights reserved" manner. The author or originator thereby gives up all rights to the work and cannot regain them.

A FAQ prepared by Creative Commons indicates that a legal difference exists between CC0 and public domain. As to a question about the Creative Commons Public Domain Dedication and Certification (PDDC) process, "The PDDC was intended to serve two purposes – to allow copyright holders to 'dedicate' a work to the public domain, and to allow people to 'certify' a work as being in the public domain." Creative Commons admits this dual purpose could lead to confusion, hence the single-purpose CC0 dedication tool.

Creative Commons promotes CC0's use because it refers to the "waiving" of rights and is supposedly more legally robust internationally (read "universal") than the PDDC, which is based more on U.S. laws that don't necessarily apply outside the U.S.