Astro is an open-source JavaScript web framework, a set of tools and conventions for building websites, designed for content-driven sites such as blogs, marketing sites and online stores. It is developed by the Astro contributors.
Astro is server-first: it renders components to HTML on the server or at build time and sends the browser lightweight HTML with no JavaScript unless a part of the page needs it. Those interactive parts are called islands; each island can be a component written in React, Vue, Svelte, Solid or another UI framework, and only its JavaScript is loaded. Content collections organize Markdown and MDX files and check their frontmatter (the metadata at the top of each file) with TypeScript types. Other built-in features include file-based routing, where the file layout of the pages folder sets the site's addresses, optimized images, view transitions between pages, and deployment adapters for Netlify, Vercel, Cloudflare, AWS and Node.js servers.
Astro is free under the MIT License; its code is on GitHub.