The Chagatai language was employed by the Central Asian Turkic States as a written language – and consequently as a diplomatic language - from the 13th century until the 19th century. It is the language in which a great variety of written records created between the 14th and 19th centuries have been preserved: chronicles, didactic (mostly Islamic) treatises, collected works of many poets such as Alisher Navoyi, stories of the lives of the saints, glossaries, grammatical studies, extensive memoirs, translations of commentaries on the Qur’an and the traditions reflecting the literary life of a region in the 15th and 16th centuries was a scene of a remarkable historical cultural phenomenon called the scene of Central Asian renaissance. It exerted significant influence on a huge region extending from Afghanistan, India, to Crimea and Caucasus in Russia. From the 19th century on, due to the fact that Central Asia was invaded and shared by the Chinese and Russian Empires, the Chagatai language began to lose influence and was replaced by regional dialects. It then split into two, becoming the two modern Turkic languages known as Uyghur and Uzbek.
The Chagatai language is not in active use today. With the emergence of national languages in the region (Uzbek, Kazak, Kighiz, Karakalpak, Tatar, and Bashkir) and the progress of literacy in the native tongues, along with the rise of national awareness among these peoples, it lost its significance as a common literary idiom of the Turks of Central Asia. Yet we cannot call Chagatai an extinct language. Its basic structure and most of its special grammatical traits continue to exist in the mentioned modern Turkic idioms. Since there were no purist of secularist language reforms to cut out Arabic and Persian elements from the vocabulary, Chagatai has remained very close to the modern dialects especially through its paremiologic content which continues an essential part of the cultural heritage of Central Asian Turks.
Chagatai works were mostly written in a slightly modified version of Arabic script. Arabic and Persian loan elements were spelled according to their Arabic and Persian orthography, differentiating between short and long vowels by the use of matres lectionis: (alif, war, and yod). In Turkish words, on the other hands, there was a tendency to mark all vowels by their equivalent Arabic characters, rather than diacritical marks, a criterion that makes Chagatai differ from Ottoman where diacritical marks were preferred in this role. The generous use of matres lectionis enables the reader to distinguish between rounded and unrounded vowels. There are no direct indicators for the reader to identify front and back vowels in Turkish graphemes where they play a distinctive role.