Islands Architecture
A rendering pattern where a page is mostly static server-rendered HTML with small, independent interactive regions (“islands”) that hydrate individually on the client. Avoids shipping/booting a JS framework for the whole page.
Why it matters here
It is how astro delivers “zero JavaScript by default” while still allowing React/Vue/Svelte components where needed — the mechanism behind Astro’s strong core-web-vitals numbers. Contrasts with the all-or-nothing client-side hydration of traditional SPA meta-frameworks (e.g. Next.js), and with eleventy‘s approach of emitting plain HTML and leaving interactivity entirely to the author (progressive enhancement).