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. Sludge is a form of manipulation. 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 and private and public institutions should regularly conduct Sludge Audits to catalogue the costs of sludge and to decide when and how to reduce it. Sludge often has costs far in excess of benefits, and it can hurt the most vulnerable members of society.