.ac is a second level domain for academic establishments, such as universities, in a number of countries, such as the United Kingdom (.ac.uk), Japan (.ac.jp), Austria (.ac.at), Belgium (.ac.be), South Africa (.ac.za), and many more. Many countries use .edu for the same purpose, for example .edu.au in Australia, .edu.my in Malaysia. Still other countries (examples include France and Switzerland), do not maintain a second level domain specifically for academic institutions. Rather, each institution will have its own second-level domain (such as sorbonne.fr for the Sorbonne, or tum.de for the Technical University of Munich). In the Domain Name System (DNS) hierarchy, a second-level domain is a domain that is directly below a top-level domain (TLD). ... “TLD” redirects here. ... .ac is the Internet country code top-level domain (ccTLD) for Ascension Island. ... A university is an institution of higher education and of research, which grants academic degrees. ... The Sorbonne, Paris, in a 17th century engraving The historic University of Paris (French: ) first appeared in the second half of the 12th century, but was in 1970 reorganised as 13 autonomous universities (University of Paris I–XIII). ... Munich University of Technology, or Technical University of Munich (TUM) (in German: Technische Universität München, TUM), is a major German university located in Munich (and the towns of Garching and Freising outside of Munich). ...

Though similar, there is a slight distinction between .edu and .ac, as .edu is generally restricted to educational institutions, whereas .ac can generally be used by any academic organization, including museums and research institutions. For nations in which .edu is used, sites for these non-educational academic organizations would reside in the .org domain instead.