What is Astro? The web framework, explained.
What is Astro? An open-source JavaScript web framework for fast, content-driven websites. It renders on the server and loads JavaScript only where a component asks for it. This page explains the architecture and the limits.
Open source, MIT licence
Free software under the MIT licence, Copyright (c) 2021 Fred K. Schott, public in the withastro/astro repository.
Server-first architecture
A multi-page architecture with server rendering. By default the entire site is prerendered and shipped as HTML.
Islands for interactivity
Interactive components are islands on an otherwise static page. Each island gets its own loading priority.
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Astro in four sentences.
What it is
- An open-source JavaScript web framework for fast, content-driven websites.
- Released under the MIT licence, currently on the Astro 7 line.
How it renders
- Server-first.
- By default the entire site is prerendered and shipped as static HTML.
- Rendering at request time is an opt-in per route.
How interactivity happens
- Through the islands architecture.
- An island is an interactive component on an otherwise static HTML page
- Everything else stays plain HTML.
Where content comes from
- content collections with a Zod schema, or a headless CMS.
- Astro is CMS-agnostic and UI-agnostic.
Astro explained plainly.
What is Astro? The short definition
Astro is an open-source JavaScript web framework for fast, content-driven websites. The project describes itself as “a JavaScript web framework optimized for building fast, content-driven websites”. That means sites whose core is content: marketing sites, blogs, magazines, documentation portals.
Astro is free software under the MIT licence, Copyright (c) 2021 Fred K. Schott, developed in the public withastro/astro repository. The current major line is Astro 7. The project follows semantic versioning, and security fixes cover exactly one previous major version, which is why an upgrade path belongs in day-to-day operation.
Server-first: what that means in practice
Astro renders components on the server and sends finished HTML to the browser. By default it removes all client-side JavaScript from components, and by default the whole site is prerendered. The delivered HTML is lean from the start.
A multi-page architecture, no single-page app
Every address has its own HTML document and the browser handles navigation. From that follows the rule of thumb we sort projects by: the more your plan is a website, the more Astro fits. The more it is an application, the more an app framework fits. For existing sites, migration to Astro describes the route.
Place Astro against your plan.
That is decided by your content model, your editorial routine and your current platform. Send us three sentences about them.
When Astro fits and when it does not.
The criteria we use to sort projects.
Astro fits when …
- The website mostly delivers content: service pages, blog, documentation, magazine, references, landing pages.
- Many similarly built pages should come from structured data: locations, products, categories, authors.
- Interactivity is the exception: a search field, a configurator, a map, a booking form.
- You want control over code and deployment: your own repository, your own hosting, no platform lock-in.
Another tool fits better when …
- Your plan is a logged-in application: roles, dashboards, live data, plenty of state in the browser. That is what custom software development is for.
- Almost every component would be interactive. Where the whole page is an island, the islands architecture loses its point: Astro vs Next.js.
- Your marketing team wants to build pages visually, without a repository and a deployment. Then Webflow is the better suggestion.
- You depend on a plugin ecosystem, a shop or a membership area for instance: Astro vs WordPress.
Frequently asked questions about Astro.
Does an Astro website need a server?
Not necessarily. By default the whole site is prerendered and static HTML pages go to the browser, which runs on any static hosting or CDN. When individual routes need to render at request time, an adapter joins the project, officially for Node, Vercel and Cloudflare, see Astro hosting.
What are Astro islands?
An island is an enhanced UI component on an otherwise static HTML page. Client islands hydrate individually in the browser, controlled by client:load, client:idle or client:visible. Server islands render independently on the server via server:defer, so the page shell can stay cached.
Can I use React in Astro?
Yes. Astro is UI-framework agnostic, with official integrations for React, Preact, Svelte, Vue, SolidJS and Alpine.js. Several frameworks can be combined, though only inside one .astro file. Without a client directive, the component renders on the server and arrives as plain HTML.
Is Astro good for SEO?
The technical groundwork is good: prerendered HTML sits in the delivered document, and built-in image optimisation derives dimensions and avoids layout shift. Rankings still come from content, structure and internal linking. What slows an existing site down shows up in an SEO audit.
Is Astro free, and what does an Astro website cost?
The framework is open source under the MIT licence, with no licence fee. Cost arises in development, content, hosting and operation, plus a headless CMS if you use one. The drivers sit under Astro development cost, and data protection under GDPR-compliant websites.
Can our marketing team publish pages without a developer?
Yes, through three combinable routes: a headless CMS with an interface and permissions, content collections with Markdown in the repository, or maintenance by chat. For that we run a WhatsApp AI agent ourselves. Structural layout changes stay development work.
Do you have a public Astro reference?
Yes, happylipo.de. We built the site in Webflow first and moved it to Astro with Sanity in September 2026. The build and the measurements are in the case study. On top of that we have our own published products and years of software development with repository and operations.
From fundamentals to implementation.
Services and operation around Astro:
Any more questions about Astro?
Write a short note about what it concerns. You get a plain answer, even when another tool turns out to be the better choice.
Ask a question about Astro.
Briefly describe what you have in mind. We answer with a read on it, never with a quote.
We usually reply within 24 hours.
Remote and on site in Germany, Austria and Switzerland. International projects on request.
From fundamentals to the build.
Astro Agency
Services, how we work and where we draw the line with Astro.
Learn moreAstro CMS & Content Collections
How the content model emerges: collections with a Zod schema or a headless CMS.
Learn moreAstro vs Next.js
The architecture question in detail: website or application, and what follows from it.
Learn more