In Islamic philosophy, irfan, and mysticism, keramat (کرامت also کرامات) is a "thaumaturgic gift" akin to the miracles of prophets.
Sufis believe that, whereas miracles can only be performed by prophets (Allah creates the miracle in support to His prophets) and are a testament to their prophethood, karaamaat are extraordinary things performed by Awliyaa' who are not prophets but are common Muslims who have reached a high rank of piety through proper knowledge of and practice of Islam, and most importantly through the constant zikr/remembrance of Allah. Allah creates the Karamaat in support to the Waliyy.
Keramats only occur by the will of Allah and the said 'wali' is not in control of them. Keramats can not be used to distinguish a truthful saint from a pseudo one. One of the greatest keramats in a saint is their ability to act upon the inward and outward traditions of Muhammad. Many keramats that have been reported and postulated by many famous sufis have no basis in Sacred Islamic Law because they have no isnad - chain of narration. The noble traditions or hadith on the other hand do contain this and they are many reports of companions of prophet Muhammad performing miraculous acts.