It was used across a wide geographic area including western or Russian Turkestan (i.e. parts of modern-day Uzbekistan, Turkmenistan, Kazakhstan, Kyrgyzstan), Eastern Turkestan (where a dialect, known as Kaşğar tılı, developed), Crimea, the Volga region (such as Tatarstan and Bashkortostan), etc.

[12] Many of the Turkic peoples, who spoke this language claimed political descent from the Chagatai Khanate.

As part of the preparation for the 1924 establishment of the Soviet Republic of Uzbekistan, Chagatai was officially renamed "Old Uzbek",[13][14][15][16][5] which Edward A. Allworth argued "badly distorted the literary history of the region" and was used to give authors such as Ali-Shir Nava'i an Uzbek identity.

Thus, Old Uzbek, Old Uyghur, Old Tatar, Old Turkmen, and a Chaghatay-influenced layer in sixteenth-century Azerbaijanian have been studied separately from each other.

It is descended from Middle Turkic, which served as a lingua franca in Central Asia, with a strong infusion of Arabic and Persian words and turns of phrase.

[citation needed] Uzbek and Uyghur, two modern languages descended from Chagatai, are the closest to it.

In 1921 in Uzbekistan, then a part of the Soviet Union, Chagatai was initially intended to be the national and governmental language of the Uzbek SSR.

[21] Up to and including the eighteenth century, Chagatai was the main literary language in Turkmenistan and most of Central Asia.

[2] [24] The manuscript of his philosophical and religious work, "Bahr ul-Khuda", written in 1508, is located in London [25] Ötemish Hajji wrote a history of the Golden Horde entitled the Tarikh-i Dost Sultan in Khwarazm.

Abu al-Ghāzī is motivated by functional considerations and describes his choice of language and style in the sentence ‘I did not use one word of Chaghatay (!

As is clear from his actual language use, he aims at making himself understood to a broader readership by avoiding too ornate a style, notably saj’, rhymed prose.

[22] Bukharan ruler Subhan Quli Khan (1680–1702) was the author of a work on medicine, "Subkhankuli's revival of medicine" ("Ihya at-tibb Subhani") which was written in the Central Asian Turkic language (Chaghatay) and is devoted to the description of diseases, their recognition and treatment.

[26] Prominent 19th-century Khivan writers include Shermuhammad Munis and his nephew Muhammad Riza Agahi.

[28][29] The following are books written on the Chagatai language by natives and westerners:[30] Sounds /f, ʃ, χ, v, z, ɡ, ʁ, d͡ʒ, ʔ, l/ do not occur in initial position of words of Turkish origin.

Examples include the alphabets of South Azerbaijani, Qashqai, Chaharmahali, Khorasani, Uyghur, Äynu, and Khalaj.

Virtually all other Turkic languages have a history of being written with an alphabet descended from Kona Yëziq, however, due to various writing reforms conducted by Turkey and the Soviet Union, many of these languages now are written in either the Latin script or the Cyrillic script.