Partial Hydration

In a traditional single-page application, the browser downloads and executes the JavaScript for every component on the page, even static ones. Partial hydrationPartial HydrationPartial hydration is a rendering technique where only the interactive components of a page are hydrated with JavaScript, instead of the entire page. ships only the JavaScript needed for the components that actually require interactivity.

It is the core mechanism behind Islands ArchitectureIslands ArchitectureIslands Architecture is a web architecture pattern where most of the page is static HTML and only specific interactive components ( and is one of the main reasons Astro sites achieve dramatically better Core Web Vitals than equivalent React or Vue SPAs.