A coaster, drink coaster, beverage coaster, or mat is an item used to rest beverages upon.
Coasters protect the surface of a table or any other surface where the user might place a beverage.
Public houses usually will have mats spread out across their tables. They are used not just to protect the surface of the table, but, as they are usually made of paper, they can also be used to absorb condensation dripping along the glass or serve as an ad-hoc notepad. mats are often branded with trademarks or alcohol advertising. mats are not to be confused with bar mats, rectangular pieces of rubber or absorbent material used to protect the counter top and soak up spilled drinks in a bar or pub.
By the mid-twentieth century, beverage coasters made in many materials and styles were being manufactured for domestic use. Today, they are common as an everyday house ware piece and as well as used in restaurants.
Coasters are often made from high gram mage paperboard, but may also be made from several layers of tissue paper. Important parameters for mats are water absorbency, wet rub and print ability.
More recently, glass coasters with empty frames have been produced. The consumer can then personalise each one with a different picture or design.