Overview of amendments

The German rules on citizenship were thoroughly revised with the entry into force of the amended Nationality Act (Staatsangehörigkeitsgesetz) on 1 January 2000. The Act was further revised with the entry into force of the main part of the Immigration Act (Zuwanderungsgesetz) on 1 January 2005 and its further provisions on 28 August 2007 and the Nationality Modernization Act (Staatsangehörigkeitsmodernisierungsgesetz) on 27 June 2024.
On 20 August 2021 the Fourth Act Amending the Nationality Act entered into force, creating a legal claim to naturalisation within the framework of reparations for persons who were affected by National Socialist persecution and therefore lost or did not obtain German citizenship but who have no entitlement to the restoration of German citizenship pursuant to Article 116 (2) sentence 1 of the Basic Law, and for their descendants. The Act also includes a ten-year right of declaration, under which children born to a German parent after the entry into force of the Basic Law who, due to the regulations in force at the time of their birth, were excluded in a gender-discriminating manner from acquiring German citizenship by descent at birth have the option of obtaining German citizenship by making a simple declaration.
You can find more detailed information here and below a summary of the most important points of the current regulations of the German Nationality Act.

Acquisition of nationality by declaration

The current law contains a right for persons, born after 24 May 1949 from a German parent but who did not acquire German nationality because of the laws in place at that time, to now acquire German nationality by declaration. The deadline to make use of this right is 19 August 2031.
You can find more information on the website of the Federal Administration Office (Bundesverwaltungsamt).

Naturalization

A naturalization while living outside of Germany is only possible in exceptional cases. Please check the website of the Federal Administration Office (Bundesverwaltungsamt) for more information.

Certificate of Retention/ Acquisition of a foreign nationality

The certificate of retention has been abolished on June 27 2024. From then on, Germans may acquire a foreign nationality by application without losing their German nationality. This regulation does not apply for cases before June 27 2024.

Non-acquision of German nationality by children born abroad / generational cut
Children, who are born outside of Germany of a German parent born him-/herself outside of German after 31 December 1999 and living abroad, do not automatically acquire German nationality if they acquire another nationality by birth. Only if a birth declaration is made for those children within one year, they will acquire German nationality.