According to the brand creator, the name "au" is based on the Japanese verbs for "meet" (会う) and "unite" (合う) (both pronounced au). However, KDDI explains that au comes from two letters which stand for few words. "A" is for access, always and amenity, and "U" is for unique, universal and user. There is also a phrase, "access to u(you)" that goes along the brand name.
The network that would eventually become au was originally set up as two networks: DDI and IDO. IDO's network was based upon the NTT Hi-cap analog cellular system, and began operations in December 1988 in the Kanto and Tokai regions. DDI's network was run by independent phone companies, and began service in 1989 using the TACS system elsewhere in Japan. Nippon Idou Tsushin (IDO) was owned by Toyota, whereas DDI was owned by Kyocera Corporation.
au K.K. (株式会社エーユー?) was established in November 2000 by the Kyocera companies as part of the DDI Cellular network. In 2001, the company was merged into KDDI (which had been formed in 2000 by the merger of DDI, KDD, and IDO), but its brand name was retained and applied to all mobile phone service under KDDI group.
au established a nationwide 3G network in 2003, replacing its previous cdmaOne service with CDMA 1X WIN (1xEV-DO Rev A) service.
EZweb: A service which provides various features for mobile phone users, including e-mail, web browsing, picture and video sharing, video conferencing, and access to location based services and games. The service runs on traditional cdmaOne mobile phone networks at a data rate of 64 kbit/s or on the new 1xEV-DO Rev A network with up to 3.1 Mbit/s downstream and 1.8 Mbit/s upstream bandwidth. In spring 2004, au became the first cellular phone based data service provider to offer an unlimited use flat-rate plan in Japan.
EZchakuuta: A service which allows users to use song segments, usually 30 seconds or less, as ring tones. Chakuuta's rights are held by Sony Music Entertainment Japan.
Chaku Uta Full: A service distributing full length songs over the mobile network. The selection offered is mainly pop music. The coding format is 48 kbit/sHE-AAC. The size of one piece of music is about 1.5 MiB. Downloaded content is secured on a memory card (miniSD, microSD, Memory Stick PRO Duo, M2) plugged into the mobile, using CPRM copy protection. Chaku-Uta Full is the trademark of Sony Music Entertainment Japan.