Qwik eliminates hydration by serializing the application state into HTML. JavaScript loads lazily on user interaction, not on page load. This means near-zero JS on initial load regardless of app complexity.
Installation
bash
# Create Qwik project with Qwik City (meta-framework)
npm create qwik@latest
cd my-app
npm install
npm run dev
Project Structure
# Qwik City project layout
src/
├── entry.ssr.tsx # SSR entry
├── root.tsx # Root component
├── global.css
├── routes/ # File-based routing
│ ├── layout.tsx # Root layout
│ ├── index.tsx # / page
│ └── articles/
│ ├── index.tsx # /articles
│ └── [slug]/
│ └── index.tsx # /articles/:slug
├── components/ # Reusable components
│ └── article-card/
│ └── article-card.tsx
└── lib/ # Utilities
Components
tsx
// src/components/article-card/article-card.tsx — Qwik component
import { component$ } from '@builder.io/qwik';
import { Link } from '@builder.io/qwik-city';
interface Props {
title: string;
slug: string;
excerpt: string;
}
export const ArticleCard = component$<Props>((props) => {
return (
<article>
<Link href={`/articles/${props.slug}`}>
<h2>{props.title}</h2>
</Link>
<p>{props.excerpt}</p>
</article>
);
});
Signals and State
tsx
// src/routes/counter/index.tsx — signals and reactivity
import { component$, useSignal, useComputed$, useTask$ } from '@builder.io/qwik';
export default component$(() => {
const count = useSignal(0);
const doubled = useComputed$(() => count.value * 2);
useTask$(({ track }) => {
track(() => count.value);
console.log(`Count changed to ${count.value}`);
});
return (
<div>
<p>Count: {count.value} (doubled: {doubled.value})</p>
<button onClick$={() => count.value++}>+1</button>
</div>
);
});
Data Loading with routeLoader$
tsx
// src/routes/articles/index.tsx — server-side data loading
import { component$ } from '@builder.io/qwik';
import { routeLoader$ } from '@builder.io/qwik-city';
import { ArticleCard } from '~/components/article-card/article-card';
export const useArticles = routeLoader$(async ({ env }) => {
const res = await fetch(`${env.get('API_URL')}/articles`);
return res.json() as Promise<Article[]>;
});
export default component$(() => {
const articles = useArticles();
return (
<div>
<h1>Articles</h1>
{articles.value.map((article) => (
<ArticleCard key={article.id} title={article.title} slug={article.slug} excerpt={article.excerpt} />
))}
</div>
);
});
Server Actions
tsx
// src/routes/articles/new/index.tsx — form with server action
import { component$ } from '@builder.io/qwik';
import { routeAction$, Form, zod$, z } from '@builder.io/qwik-city';
export const useCreateArticle = routeAction$(
async (data, { redirect, env }) => {
const res = await fetch(`${env.get('API_URL')}/articles`, {
method: 'POST',
headers: { 'Content-Type': 'application/json' },
body: JSON.stringify(data),
});
if (!res.ok) return { success: false, error: 'Failed to create' };
throw redirect(302, '/articles');
},
zod$({
title: z.string().min(1).max(200),
body: z.string().min(1),
})
);
export default component$(() => {
const action = useCreateArticle();
return (
<Form action={action}>
<input name="title" placeholder="Title" required />
<textarea name="body" placeholder="Body" required />
<button type="submit">Create</button>
{action.value?.error && <p>{action.value.error}</p>}
</Form>
);
});
Layouts
tsx
// src/routes/layout.tsx — root layout
import { component$, Slot } from '@builder.io/qwik';
import { Link } from '@builder.io/qwik-city';
export default component$(() => {
return (
<div>
<header>
<nav>
<Link href="/">Home</Link>
<Link href="/articles">Articles</Link>
</nav>
</header>
<main>
<Slot />
</main>
</div>
);
});
Middleware
tsx
// src/routes/admin/layout.tsx — auth middleware via onRequest
import { type RequestHandler } from '@builder.io/qwik-city';
export const onRequest: RequestHandler = async ({ cookie, redirect }) => {
const token = cookie.get('session')?.value;
if (!token) throw redirect(302, '/login');
};
useStore for Complex State
tsx
// src/routes/dashboard/index.tsx — store for nested reactive state
import { component$, useStore, $ } from '@builder.io/qwik';
export default component$(() => {
const state = useStore({
articles: [] as Article[],
filter: '',
loading: false,
});
const fetchArticles = $(async () => {
state.loading = true;
const res = await fetch('/api/articles');
state.articles = await res.json();
state.loading = false;
});
return (
<div>
<button onClick$={fetchArticles}>Load</button>
<input bind:value={state.filter} placeholder="Filter..." />
{state.loading ? <p>Loading...</p> : (
state.articles
.filter((a) => a.title.includes(state.filter))
.map((a) => <div key={a.id}>{a.title}</div>)
)}
</div>
);
});
Deployment
bash
# Add deployment adapter
npm run qwik add cloudflare-pages # or: vercel, netlify, node-server, deno
npm run build
npm run deploy
Key Patterns
- Use
$suffix on functions (onClick$,component$,routeLoader$) — it marks serialization boundaries - Use
useSignalfor primitives,useStorefor objects — similar to Solid's signal/store split routeLoader$runs on the server during SSR — data is serialized into HTMLrouteAction$handles form submissions server-side with Zod validation- JavaScript loads lazily per interaction — no hydration step
- Use
onRequesthandlers in layouts for server-side middleware (auth, redirects) - Deploy anywhere: Cloudflare, Vercel, Netlify, Deno, Node — via adapters