What is CC0 (Creative Commons Zero)?
Besides licences, Creative Commons also offers CC0 (Creative Commons Zero) for use. With CC0, rights holders can waive all rights to a work and release the work for unconditional use. It is however explicitly not another licence but is referred to accordingly as the CC0 dedication. In contrast to the most open Creative Commons licence CC BY, the condition of attribution is also not required here. A work with the CC0 dedication can be used, edited, distributed, and published for any legal purpose; its use is not restricted in any way by licence conditions.
However, CC0 should not be confused with a work being in the public domain. In the case of works in the public domain, copyright protection has expired or did not exist in the first place due to a lack of originality or due to a legal exception. The CC0 dedication can be used for a copyrighted work to release it for use equivalent to the public domain. CC0 was designed in such a way that it can be used worldwide in different jurisdictions. Since a waiver of copyright protection is not possible under German copyright law, CC0 is equivalent to a waiver of all possible rights and legal claims by the creator. By contrast, in American copyright law, for example, authors can waive copyright for a work and release it into the public domain; in that case, CC0 means exactly that.
In science, CC0 is particularly suitable for content for which unconditional use by third parties is acceptable or advantageous for common use purposes (e.g., charts and graphics) as well as for content for which copyright protection may not even apply in the first place or where attribution to a work would lead to impractical or close to impossible efforts (e.g., research data).