What is the difference between public domain and CC0 release?

Public domain refers to the legal status of intellectual property. Works in the public domain are works for which no copyrights exist: either (1) because they have never existed, (2) because the protection of these rights has expired or (3) because rights holders have waived their copyrights in favor of the general public. The use of such works is possible without restriction.

While the first two variants of public domain mentioned in 1-2 above can also be found in Germany, a complete waiver of copyright (see 3 above) is not possible in Germany and other European countries. Moral rights - the right to acknowledge authorship and the right of first publication - as the core of copyright cannot be waived in Germany. Works protected by copyright can therefore not be transferred to the public domain by means of a declaration of waiver. The Anglo-American equivalent for 1 and 2 is Public Domain Mark; for 3 - Public Domain Declaration.

For those who wish to release their work for use by the general public in Germany, the CC Zero release instrument is suitable. This is a waiver by the rights holder to exercise their copyrights vis-à-vis the users. After the CC Zero release, the work may be used unconditionally - as with the public domain. In particular, no information about the license and legal ownership of the material needs to be provided.

The main difference between the CC Zero release and the public domain release is that in the case of a CC Zero release, the rights holders only waive the exercise of their copyrights - their assertion by way of a warning or in court - but not the moral rights themselves, as in the case of the public domain release.