Owing to the small quantity of carbon dioxide (CO2) that can be emitted before we exceed the 1.5°C–2°C target of the Paris Agreement on climate change, we are increasingly likely to require ways of removing significant CO2 from the atmosphere. In addition to the biological options considered to date such as afforestation and bioenergy with CO2 capture, direct air carbon capture and sequestration (DACCS) is emerging as a potentially important synthetic CO2 removal technology. Here, we explain how DACCS works, focusing on two major processes that have been developed into large-scale pilot plants. We discuss cost estimates and operational energy requirements, as well as ecological and ethical considerations. We highlight the role of DACCS in the low-carbon transition by discussing its benefits, while also noting potential trade-offs and uncertainties that deserve further investigation.