What are Nuxt layers and how do they enable code sharing?

Nuxt Layers are a composable architecture feature where multiple Nuxt applications or packages can be stacked, with each layer contributing its own pages, components, composables, server routes, and config. Layers are defined in nuxt.config.ts under extends: ['./base-layer', 'npm:my-layer-package']. The final application merges all layers, with closer layers overriding deeper ones. This enables powerful patterns: a design system layer providing shared components, a CMS layer providing content-fetching composables, or a monorepo base layer with shared utilities. Each layer is itself a valid Nuxt project. Layers can be local directories, Git repositories, or npm packages, making them the Nuxt equivalent of platform-level code sharing.