The seven eponymous reciters recognized as the sources of the canonical qira'at were each based in one of the major early centers of Islamic learning: Nafi in Medina, Ibn Kathir in Mecca, Abu Amr in Basra, Ibn Amir in Damascus, and Asim, Hamzah and Al-Kisai, all three associated with Kufa, so that the seven readings between them represent the major regional centers of the early Muslim world rather than a single locality's tradition.
The scholar Ibn Mujahid, writing in Baghdad in the early tenth century, is generally credited with formally selecting and canonizing these seven readers' traditions as the standard recognized set, a consolidation that closed off what had been a wider and less settled range of transmitted variant readings circulating up to that point. Each of the seven readers is in turn associated with two principal onward transmitters, so the tradition speaks properly of fourteen riwayat, individual transmitted readings, descending from the seven named systems, a genealogical structure comparable in shape, though entirely separate in content, to the branching shakha system that preserves the Vedas. Some later scholarship extended recognition to three additional readers beyond the original seven, producing a wider set of ten canonically accepted readings, though the seven remain the core and most widely referenced grouping.