Trick-or-treating is a traditional Halloween custom for children and adults in some countries. During the evening of Halloween, on October 31, people in costumes travel from house to house, asking for treats with the phrase "trick or treat". The "treat" is some form of confectionery, usually candy/sweets, although in some cultures money is given instead. The "trick" refers to a threat, usually idle, to perform mischief on the resident(s) or their property if no treat is given. Some people signal that they are willing to hand out treats by putting up Halloween decorations outside their doors; houses may also leave their porch lights on as a universal indicator that they have candy; some simply leave treats available on their porches for the children to take freely, on the honor system.

Halloween or Hallowe'en is a celebration observed in many countries on 31 October, the eve of the Western Christian feast of All Hallows' Day. It is at the beginning of the observance of Allhallowtide, the time in the liturgical year dedicated to remembering the dead, including saints (hallows), martyrs, and all the faithful departed. In popular culture, the day has become a celebration of horror, being associated with the macabre and supernatural.