To support carbon markets, regulators must engage in a continuous process of learning. This article explores offsets regulation in the compliance markets of Europe, the United States and China, alongside the Clean Development Mechanism, to identify what has been learnt since offsets were initiated. We argue that offsets regulation must learn to work with demands for commercial viability, environmental sustainability and political legitimacy. We find that the learning here recommends greater control of the shares, sectors, sources and standards of offsets than was initially chosen. The findings provide some cautious optimism about the scope for improvements to such market mechanisms.