Web3 describes a group of technologies for managing collective interactions on the internet while avoiding centralised control, granting users agency over access to their data, and managing distribution of value as digital assets. The technologies are distributed ledgers including blockchain, cryptocurrencies, distributed autonomous organisations, decentralised finance, and non-fungible tokens. Web3 technologies offer technical solutions to problems of trust and verifiability online. Their open source basis makes them available to developers globally and across sectors and communities. Some of these technologies are already in use across many sectors and have been proposed as applicable to a much greater range of uses in the future. If the technologies prove successful sustainably at scale for a very wide range of functions, they might change and expand what the internet delivers for a high proportion of users, and genuinely warrant the description Web3.