A sleep sack is a wearable blanket designed for infants and toddlers to keep them warm and safe while sleeping. Unlike traditional blankets, sleep sacks have armholes and a zipper or snap closure, allowing babies to move their legs freely while preventing them from getting tangled or covered by loose fabric. Sleep sacks come in various materials and thicknesses, making them suitable for different temperatures. They are often used as an alternative to blankets, reducing the risk of SIDS (Sudden Infant Death Syndrome) by ensuring that babies remain covered without the hazards of loose bedding.