A karkashin Boris I, Bulgaria ta zama Kirista a hukumance, kuma Ecumenical Patriarch ya yarda ya ba da izinin Archbishop Bulgarian mai cin gashin kansa a Pliska.Masu wa’azin bishara daga Constantinople, Cyril da Methodius , sun ƙirƙira haruffan Glagolitic, waɗanda aka karɓa a cikin daular Bulgaria a kusa da 886. Baƙaƙe da tsohon harshen Bulgarian wanda ya samo asali daga Slavonic ^[27] ya haifar da ingantaccen ayyukan adabi da al'adu waɗanda ke kewaye da Preslav. da Makarantun Adabi na Ohrid, wanda aka kafa bisa tsari na Boris I a 886.A farkon karni na 9, an kirkiro sabon haruffa - Cyrillic - a Makarantar adabi na Preslav, wanda aka saba da harafin Glagolitic da Saints Cyril da Methodius suka kirkira.^[28] Wata madaidaicin ka'idar ita ce, Saint Climent na Ohrid, wani masani dan Bulgaria kuma almajirin Cyril da Methodius ne ya kirkiro haruffa a Makarantar Adabi ta Ohrid.