Islands Architecture renders most of the page as static HTML, while only small, isolated interactive regions (islands) ship JavaScript and hydrate independently, dramatically reducing client-side JavaScript and improving performance [citation:3].
Islands Architecture is a modern rendering pattern that addresses the problem of excessive JavaScript in traditional full-hydration applications. In this pattern, the server renders the entire page as HTML, but only the interactive components (called islands) load and hydrate their JavaScript. Islands load independently and can have different hydration strategies (eager, on-viewport, on-interaction). This approach significantly reduces the amount of JavaScript shipped to the client and improves performance, especially on content-heavy sites like blogs, documentation, and e-commerce product pages. Astro is the most prominent framework implementing this pattern, but it can be built manually [citation:3].