The company was founded by three entrepreneurs, Martin Ostermayer, Thorsten Rehling and Dirk Freise in 2005.

Blau Mobilfunk took over the mobile virtual network operator in the discount sector, debitel-light, in November 2006.

Debitel received a minority share of the Blau Mobilfunk GmbH as compensation.

[4] Blau.de also offered an allnet flatrate like Yourfone in addition to normal prepaid cards in 2012.

[5] It became a brand of Telefonica Germany, which after the E-Plus acquisition in 2014 migrated customers to their main company in 2015.