United Internet AG, through its subsidiaries, operates as an Internet service provider.

The company operates through Consumer Access, Business Access, Consumer Applications, and Business Applications segments.

It offers landline-based broadband and mobile internet products, including home networks, online storage, telephony, and IPTV for private users; and telecommunication products ranging from fiber-optic direct connections to tailored ICT solutions, which include voice, data, and network solutions, as well as infrastructure services to national and international carriers and ISPs. The company also provides ad-financed and fee-based application products for consumer and business customers, including domains, websites, web hosting, servers, cloud solutions, and e-shops; personal information management applications, such as email, to-do lists, appointments, and addresses; and group works, online storage, and office software.

It offers its access products through the yourfone, smartmobile.de, 1&1, and 1&1 versatel brands; and applications through GMX, mail.com, WEB.DE, home.pl, Arsys, STRATO, IONOS, Fasthosts, InterNetX, united-domains, and World4You brand names.

In addition, the company offers customers professional services in the fields of active domain management under the Sedo brand; and online advertising services under the United Internet Media brand name.

It has operations in Germany, the United States, the United Kingdom, Spain, France, Poland, Italy, Austria, Hungary, Romania, Bulgaria, the Czech Republic, Slovakia, the Netherlands, Switzerland, Canada, and Mexico.

The company was founded in 1988 and is headquartered in Montabaur, Germany.