Layer 2 & Scaling

Beyond Lightning, a wide range of systems are presented as Bitcoin "Layer 2s" — Liquid, Rootstock, Stacks, BitVM, Babylon, Fedimint and Cashu — yet the label itself has no agreed technical definition. More useful than speed or smart-contract capability are two questions: who can cause you to lose funds (the trust assumption), and can you exit on-chain without that party's consent. This article defines the categories first, then contrasts each project's trust assumptions in a comparison table.