Old Uyghur

The Old Uyghur script developed from the cursive variant of Sogdian script around the 8th century. It was widely used to write the Old Uyghur language by the people who inhabited the Tarim Basin in northwestern China. Over time, it spread to many regions of Asia and was used for Chinese, Mongolian, Tibetan, and Arabic languages. It also served as the basis for the Old Mongolian script. By the 16th century, it was replaced by the Arabic script due to the Uyghurs' conversion to Islam.

Formally, the Old Uyghur alphabet is consonantal. However, it includes what are known as matres lectionis, which are consonant letters that represent long vowel sounds. The writing is done vertically, from top to bottom, and the columns go from right to left.