Distribution of the Cyrillic script worldwide. The dark green shows the countries that use Cyrillic as the one main script; the lighter green those that use Cyrillic alongside another official script. Numerous Cyrillic alphabets are based on the Cyrillic script. The early Cyrillic alphabet was developed in the First Bulgarian Empire during the 9th century AD at the Preslav Literary School by the disciples of the Byzantine theologians Cyril and Methodius.