The single most consequential fact about this region's speech is that the Kauravi of the Upper Doab, together with the speech of the Delhi region, is the base on which both modern standard Hindi and modern standard Urdu were built. Two national standards and a body of literature read by half a billion people rest on the everyday dialect of a cane-growing plain — and the plain itself has largely stopped being credited for it, because the standard is now simply called Hindi.
Kauravi (Khari Boli)Indo-Aryan, Western Hindi
Spoken from Saharanpur to Bulandshahr. Khari Boli is the base of standard Hindi and Urdu; Kauravi is what its speakers actually speak, and it is noticeably blunter, with a different verb ending and a strong Punjabi and Haryanvi overlay in the north-west.
KanaujiIndo-Aryan, Western Hindi
The Central Doab variety of Kannauj, Farrukhabad, Etawah and Kanpur — transitional between Braj and Awadhi, and almost always recorded in the census as Hindi.
Braj Bhasha of the western marginIndo-Aryan, Western Hindi
Spoken along the Yamuna in Aligarh, Hathras and Mainpuri, where the Doab faces Braj across the river.
Prayag transitional speechIndo-Aryan
At the confluence the region meets Awadhi, Bagheli and Bhojpuri at once, and the city speech is a standardised Hindi with features from all three.
Doabi Urdu of the qasbahsIndo-Aryan, Hindustani
The register of Aligarh, Kannauj, Deoband and the smaller Muslim towns, sustained by a dense network of madrasas and by Aligarh Muslim University.