Progressive Hydration
Hydrate only the parts of the page that need interactivity for faster TTI.
Progressive Hydration is a free Sveltejs Academy lesson on CoddyKit. This is lesson 4 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Sveltejs Academy learning path, and your progress syncs across the web and the CoddyKit app. The Sveltejs Academy course includes 4 lessons in total.
What Hydration Is
Hydration is the process of attaching JS behavior to server-rendered HTML in the browser.
Why Progressive
Full hydration of large pages costs CPU. Progressive hydration prioritizes critical interactivity first.
SvelteKit Defaults
SvelteKit hydrates per page, not per component. Routes are independently hydrated as needed.
Island Architecture
Combine static prerender with selective hydration of interactive components only.
Lazy Components
Use dynamic import() for non-critical components to defer loading.
const Comments = await import("./Comments.svelte");Intersection Observer
Hydrate below-the-fold widgets when they scroll into view.
Use Actions
Wrap lazy loading in a Svelte action for reusability.
Performance Wins
Lower TTI, smaller initial JS payload, faster initial interactivity.
Trade-offs
Deferred hydration may delay interactivity for the deferred parts. Plan carefully.
SSR + Hydration
SSR provides the initial paint; hydration adds the JS behavior on top.
Frameworks Compared
Astro and Qwik popularized island/resumable approaches; SvelteKit gives you similar tools manually.
Quick Check
What is progressive hydration?
Recap
Defer hydration of non-critical components using dynamic imports and intersection observers for faster TTI.
Learn HTML with an AI tutor — free
Write and run real code in your browser, get instant help from a 24/7 AI tutor, and pick up where you left off on the web or in the app.
- Courses
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Frequently Asked Questions
Is the “Progressive Hydration” lesson free?
Yes — the full text of “Progressive Hydration” is free to read here on the web. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Sveltejs Academy course, upgrade to CoddyKit PRO. The Sveltejs Academy course includes 4 lessons in total.
What will I learn in “Progressive Hydration”?
Hydrate only the parts of the page that need interactivity for faster TTI. You practise Sveltejs Academy with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start Sveltejs Academy?
No prior experience is required. Sveltejs Academy on CoddyKit is structured for beginners through advanced learners, so you can start here or from the beginning and move at your own pace. This is lesson 4 of 4.
How long does the “Progressive Hydration” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this Sveltejs Academy lesson?
Yes. Every Sveltejs Academy lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- Streaming Data with Promises in load
- Deferred Loading and Suspense-Like UX
- Streaming from Server with +server.js
- Progressive Hydration