Serfs were usually completely free to leave their lord’s land.

The story behind the answer

Most serfs were legally bound to their lord’s manor, owing labor services and dues in exchange for protection and the right to farm strips of land. Leaving, marrying, or apprenticing often required the lord’s permission and sometimes fees, with obligations enforced in the manorial court. They weren’t chattel slaves, but their freedom of movement and economic choices were tightly constrained.

There were paths to greater freedom: manumission (buying release), gradual commutation of labor services into rent, or—in some regions—escaping to a chartered town where “town air makes free” after a year and a day. After the Black Death reduced the labor force, surviving peasants gained bargaining power, accelerating these changes and helping spark uprisings like the English Peasants’ Revolt of 1381.