What are the key differences between Nuxt.js and Vue.js?

Vue.js is a UI library/framework for building reactive user interfaces, while Nuxt.js is a full-stack meta-framework built on top of Vue. Vue alone is a client-side rendering framework by default — you manage routing, state, and build configuration yourself. Nuxt adds file-based routing, SSR/SSG, auto-imports for components and composables, a built-in server with API routes, and integrations with modules like Pinia, i18n, and Nuxt Content. In short, Nuxt provides a complete opinionated application structure, whereas Vue is just the rendering layer.