Ernst & Young (EY) is a consulting firm based in London, United Kingdom that ernst & young, known as ey, is one of the big four professional services firms providing assurance, tax, consulting and strategy and transactions services. it operates as a global network of member firms across more than 150 countries with about 400,000 people and revenues over 51 billion dollars. ey has an established blockchain practice focused on enterprise tokenization and privacy. its technologies include nightfall, a zero knowledge rollup for private transactions on ethereum, starlight for private smart contract business logic, and the opschain suite for traceability, esg and contract management. in april 2025 ey released nightfall_4, replacing the optimistic rollup with a zero knowledge version. They serve clients in Global. Ernst & Young (EY) is listed on The Token Playbook's vetted provider registry at thetokenplaybook.com/registry/ernst-young-ey.