There are six main dialects: Sahidic, Bohairic, Fayumic, Oxyrhynchite (Middle Egyptian), Akhmimic, and Lycopolitan (Subakhmimic). The number of Coptic dialects has increased with the discovery of more Coptic and the intensive research in Coptic dialects, especially in the second half of the 20th century. However, locating the dialects geographically remains a matter of contention, simply because the provenance of the vast majority of Coptic manuscripts is uncertain.

Almost all original Coptic literature was written in Sahidic, which is a literary standard dialect because of its dialectal neutrality as it shares many features with the other dialects. The oldest Sahidic dates from the third century. Most of the dialects are not attested in literary texts beyond the sixth century.

Fayumic was in continual use in documents until the 9th or 10th century. Sahidic texts were copied as late as the early 11th century, when it was supplanted by Bohairic. The latter was the dialect of western Delta and the of Wadi al-Natrun. is still in use today in the liturgy of the Coptic Church.