Which language was mostly used for the propagation of Buddhism?

Pali is a Middle Indo-Aryan language (of Prakrit group) of the Indian subcontinent. It is best known as the language of many of the earliest extant Buddhist scriptures. as collected in the Pali Canon or Tip taka, and as the liturgical language of Theravada Buddhism. Pali is a literary language of the Prakrit language family.