Astro Patterns

SDK: @clerk/astro v3+. Requires Astro 4.15+.

What Do You Need?

Task	Reference
Configure middleware	references/middleware.md
Protect SSR pages	references/ssr-pages.md
Use Clerk in island components	references/island-components.md
Auth in API routes	references/api-routes.md
Use Clerk with React in Astro	references/astro-react.md

Mental Model

Astro has two rendering modes per page: SSR and static prerender. Clerk works differently in each:

• SSR pages — use Astro.locals.auth() which is populated by the middleware
• Static pages (export const prerender = true) — Clerk middleware skips them; use client-side hooks in islands
• Islands — React/Vue/Svelte components; use useAuth() and other hooks from @clerk/astro/react

Request → clerkMiddleware() → SSR page → Astro.locals.auth()
                                ↓
                         Island (.client) → useAuth() hook

Setup

astro.config.mjs

import { defineConfig } from 'astro/config'
import clerk from '@clerk/astro'

export default defineConfig({
  integrations: [clerk()],
  output: 'server',
})

src/middleware.ts

import { clerkMiddleware, createRouteMatcher } from '@clerk/astro/server'

const isProtectedRoute = createRouteMatcher(['/dashboard(.*)'])

export const onRequest = clerkMiddleware((auth, context, next) => {
  if (isProtectedRoute(context.request) && !auth().userId) {
    return auth().redirectToSignIn()
  }
  return next()
})

SSR Page Auth

---
const { userId, orgId } = Astro.locals.auth()
if (!userId) return Astro.redirect('/sign-in')
---

<h1>Dashboard</h1>

Common Pitfalls

Symptom	Cause	Fix
Astro.locals.auth is undefined	Missing middleware	Add clerkMiddleware to src/middleware.ts
Auth works in dev but not production	output: 'static' globally	Set output: 'server' or hybrid for protected pages
Static page has no auth	Prerendered pages skip middleware	Use export const prerender = false or move to island
Island not reactive to sign-in	Missing client:load directive	Add client:load to the island component

Import Map

What	Import From
clerkMiddleware, createRouteMatcher	@clerk/astro/server
useAuth, useUser, UserButton	@clerk/astro/react
Astro components (<SignIn>, etc.)	@clerk/astro/components

Env Variables

# .env
PUBLIC_CLERK_PUBLISHABLE_KEY=pk_...
CLERK_SECRET_KEY=sk_...

Astro uses PUBLIC_ prefix for client-exposed variables (not NEXT_PUBLIC_).

See Also

• clerk-setup - Initial Clerk install
• clerk-custom-ui - Custom flows & appearance
• clerk-orgs - B2B organizations

Docs

Astro SDK