In the wizarding world, a password is a secret word or phrase used to gain access to a location that is magically guarded or concealed. This security measure is most prominently featured at Hogwarts School of Witchcraft and Wizardry, where it is used to protect the entrances to three of the four House common rooms and the Headmaster's office. Typically, a password must be spoken aloud to a magical guardian, such as an enchanted portrait or a stone gargoyle. If the correct password is provided, the guardian will permit entry by moving aside to reveal the hidden entrance. The use of passwords serves not only as a security measure against intruders but also as a means of ensuring privacy for the area's inhabitants. Passwords for Hogwarts common rooms are changed regularly to maintain security. This method contrasts with the access requirements for other Hogwarts locations. For instance, the Ravenclaw Tower entrance requires answering a philosophical riddle posed by a bronze eagle knocker, while the Hufflepuff common room is accessed by tapping a specific barrel in the rhythm of 'Helga Hufflepuff'.
The entrance to the Gryffindor common room is guarded by the portrait of the Fat Lady, who requires the correct password before swinging open. She was briefly replaced by Sir Cadogan after being attacked by Sirius Black.
The entrance to the Slytherin dungeon is a bare, damp stretch of stone wall. Speaking the password causes a concealed stone door to slide open.
The entrance to the Headmaster's office is protected by a large and imposing stone gargoyle that springs to life and moves aside when given the correct password. Albus Dumbledore's passwords were traditionally the names of his favourite Muggle sweets.
Located on the fifth floor of Hogwarts Castle, the entrance to the Prefects'' bathroom is a white marble door that requires a password.
The password system at Hogwarts is a core part of student life. New passwords are given out by Prefects or the Head Boy and Head Girl and are expected to be memorized by all students of a given House. The system's main vulnerability is human error. Neville Longbottom was notoriously forgetful and often had to wait for other students to let him into Gryffindor Tower. In his third year, he wrote the passwords down on a list, which was subsequently stolen by Crookshanks and given to Sirius Black. This security breach allowed Sirius to enter the Gryffindor common room and attack Ron Weasley's bed, demonstrating the critical importance of keeping passwords secret. Following this incident, the Fat Lady was reinstated as guardian with additional security trolls.