A duvet is a type of soft bedding filled with natural or synthetic insulating material, designed to keep the sleeper warm during the night. Also known as a comforter in some countries, a duvet is typically used without a top sheet and covered in a removable duvet cover for easy washing. It is a central element of the sleep environment and has a significant influence on sleep comfort and temperature regulation. Duvets are available in a range of fill materials, each with different properties. Down duvets, filled with the soft underfeathers of ducks or geese, are prized for their exceptional warmth-to-weight ratio, lightness, and breathability, making them ideal for regulating body temperature during sleep. Synthetic-fill duvets are a more affordable and hypoallergenic alternative, suitable for those with feather allergies. Wool duvets are naturally temperature-regulating, moisture-wicking, and resistant to dust mites. Silk duvets are lightweight and hypoallergenic, offering a luxurious feel. The warmth of a duvet is measured in tog ratings. A low tog rating (1.5–4.5) indicates a lightweight summer duvet suitable for warmer months, while a higher tog rating (10.5–15) provides greater warmth for cold winter nights. Many people opt for a combination of two duvets with different tog ratings that can be used separately or together, providing flexibility across the seasons. Choosing the right duvet for your individual warmth needs and sleeping environment can make a meaningful difference to the quality of your sleep. A duvet that is too warm may cause overheating and disrupt sleep, while one that is too cool may lead to frequent waking.