This briefing considers arguments for and against UBI and examines what can be learned from efforts to realise it in practice. It describes different meanings and versions of UBI, reasons why people are attracted to the idea, likely costs of implementing UBI, arguments against it, practical trials in poor, middle-income and rich countries, and what evidence they yield. It brief-ly describes a range of alternative policies for tackling today’s urgent chal-lenges, and ends by concluding that UBI is unlikely to fulfil the claims that progressive advocates make for it and that there are more effective ways of tackling the problems they seek to address.