The Hogwarts uniform is the clothing that students attending Hogwarts School of Witchcraft and Wizardry are required to wear. The uniform must be worn every day in every lesson, and kept on while in the Great Hall, Study Hall, Common Room or Library. They may wear casual clothing when they have the day, or the rest of the day, free. The uniform is washed in the laundry, which is located somewhere in Hogwarts Castle and presumably operated by house-elves.