Kara-Khanid Khanate
The "modern" Uyghur language is not descended from Old Uyghur; rather, it is a descendant of the Karluk languages spoken by the Kara-Khanid Khanate, in particular the "Xākānī" language described by Mahmud al-Kashgari while Western Yugur is considered to be the true descendant of Old Uyghur and is also called "Neo-Uygur" according to Gerard Clauson.