The UK Competition and Markets Authority has launched a public consultation on the potential harms to competition and consumers caused by the deliberate or unintended misuse of algorithms. A paper accompanying the consultation explores harms such as the personalisation of prices and other aspects of online choice architecture, the potential of algorithms to facilitate collusion, and the use of algorithms to exclude competitors. The paper also looks at the role of regulators in addressing such harms, for instance through setting standards and facilitating better accountability of algorithmic systems. The input received during the consultation -open until 16 March 2021 -will be used to inform the authority's work in digital markets, including its programme on analysing algorithms and the operation of the recently announced Digital Markets Unit.