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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() hookSetup
astro.config.mjs
ts
import { defineConfig } from 'astro/config'
import clerk from '@clerk/astro'
export default defineConfig({
integrations: [clerk()],
output: 'server',
})src/middleware.ts
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
astro
---
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 installclerk-custom-ui- Custom flows & appearanceclerk-orgs- B2B organizations
