Abstract: Consumers, employees, students, and others are often subjected to “sludge”: excessive or unjustified frictions, such as paperwork burdens, that cost time or money; that may make life difficult to navigate; that may be frustrating, stigmatizing, or humiliating; and that might end up depriving people of access to important goods, opportunities, and services. Because of behavioral biases and cognitive scarcity, sludge can have much more harmful effects than private and public institutions anticipate. To protect consumers, investors, employees, and others, firms, universities, and government agencies should regularly conduct Sludge Audits to catalogue the costs of sludge, and to decide when and how to reduce it. Much of human life is unnecessarily sludgy. Sludge often has costs far in excess of benefits, and it can have hurt the most vulnerable members of society.