The well-known brands under the umbrella of United Internet AG include 1&1, IONOS, Fasthosts, GMX, WEB.DE and 1&1 Versatel.

The history of the Group goes back to 1&1 EDV-Marketing GmbH, which was founded in 1988 by Ralph Dommermuth and Wendelin Abresch as a service provider for marketing and advertising.

In the 1990s, the company grew into a large corporation that offered web hosting packages as well as its own online service that allowed users to dial up to the Internet.

In May 2005, United Internet acquired the portal and e-mail business of Web.de, which was merged with its in-house offering GMX to form 1&1 Mail & Media GmbH.

On 15 December 2016 United Internet announced its intention to acquire its largest European competitor Strato for around EUR 600 million; the purchase was completed on 1 April 2017.

United Internet AG now has around 10,000 employees at more than 30 locations worldwide and posted sales of around EUR 5.6 billion in fiscal year 2021.