auth

Authentication integration guidance — Clerk (native Vercel Marketplace), Descope, and Auth0 setup for Next.js applications. Covers middleware auth patterns, sign-in/sign-up flows, and Marketplace provisioning. Use when implementing user authentication.

Authentication Integrations

You are an expert in authentication for Vercel-deployed applications — covering Clerk (native Vercel Marketplace integration), Descope, and Auth0.

Clerk (Recommended — Native Marketplace Integration)

Clerk is a native Vercel Marketplace integration with auto-provisioned environment variables and unified billing. Current SDK: @clerk/nextjs v7 (Core 3, March 2026).

Install via Marketplace

# Install Clerk from Vercel Marketplace (auto-provisions env vars)
vercel integration add clerk

Auto-provisioned environment variables:

CLERK_SECRET_KEY — server-side API key
NEXT_PUBLIC_CLERK_PUBLISHABLE_KEY — client-side publishable key

SDK Setup

# Install the Clerk Next.js SDK
npm install @clerk/nextjs

Middleware Configuration

// middleware.ts
import { clerkMiddleware } from "@clerk/nextjs/server";

export default clerkMiddleware();

export const config = {
  matcher: [
    // Skip Next.js internals and static files
    "/((?!_next|[^?]*\\.(?:html?|css|js(?!on)|jpe?g|webp|png|gif|svg|ttf|woff2?|ico|csv|docx?|xlsx?|zip|webmanifest)).*)",
    // Always run for API routes
    "/(api|trpc)(.*)",
  ],
};

Protect Routes

// middleware.ts — protect specific routes
import { clerkMiddleware, createRouteMatcher } from "@clerk/nextjs/server";

const isProtectedRoute = createRouteMatcher(["/dashboard(.*)", "/api(.*)"]);

export default clerkMiddleware(async (auth, req) => {
  if (isProtectedRoute(req)) {
    await auth.protect();
  }
});

Frontend API Proxy (Core 3)

Proxy Clerk's Frontend API through your own domain to avoid third-party requests:

// middleware.ts
export default clerkMiddleware({
  frontendApiProxy: { enabled: true },
});

Provider Setup

// app/layout.tsx
import { ClerkProvider } from "@clerk/nextjs";

export default function RootLayout({
  children,
}: {
  children: React.ReactNode;
}) {
  return (
    <ClerkProvider>
      <html lang="en">
        <body>{children}</body>
      </html>
    </ClerkProvider>
  );
}

Sign-In and Sign-Up Pages

// app/sign-in/[[...sign-in]]/page.tsx
import { SignIn } from "@clerk/nextjs";

export default function Page() {
  return <SignIn />;
}

// app/sign-up/[[...sign-up]]/page.tsx
import { SignUp } from "@clerk/nextjs";

export default function Page() {
  return <SignUp />;
}

Add routing env vars to .env.local:

NEXT_PUBLIC_CLERK_SIGN_IN_URL=/sign-in
NEXT_PUBLIC_CLERK_SIGN_UP_URL=/sign-up

Access User Data

// Server component
import { currentUser } from "@clerk/nextjs/server";

export default async function Page() {
  const user = await currentUser();
  return <p>Hello, {user?.firstName}</p>;
}

// Client component
"use client";
import { useUser } from "@clerk/nextjs";

export default function UserGreeting() {
  const { user, isLoaded } = useUser();
  if (!isLoaded) return null;
  return <p>Hello, {user?.firstName}</p>;
}

API Route Protection

// app/api/protected/route.ts
import { auth } from "@clerk/nextjs/server";

export async function GET() {
  const { userId } = await auth();
  if (!userId) {
    return Response.json({ error: "Unauthorized" }, { status: 401 });
  }
  return Response.json({ userId });
}

Descope

Descope is available on the Vercel Marketplace with native integration support.

Install via Marketplace

vercel integration add descope

SDK Setup

npm install @descope/nextjs-sdk

Provider and Middleware

// app/layout.tsx
import { AuthProvider } from "@descope/nextjs-sdk";

export default function RootLayout({
  children,
}: {
  children: React.ReactNode;
}) {
  return (
    <AuthProvider projectId={process.env.NEXT_PUBLIC_DESCOPE_PROJECT_ID!}>
      <html lang="en">
        <body>{children}</body>
      </html>
    </AuthProvider>
  );
}

// middleware.ts
import { authMiddleware } from "@descope/nextjs-sdk/server";

export default authMiddleware({
  projectId: process.env.DESCOPE_PROJECT_ID!,
  publicRoutes: ["/", "/sign-in"],
});

Sign-In Flow

"use client";
import { Descope } from "@descope/nextjs-sdk";

export default function SignInPage() {
  return <Descope flowId="sign-up-or-in" />;
}

Auth0

Auth0 provides a mature authentication platform with extensive identity provider support.

SDK Setup

npm install @auth0/nextjs-auth0

Configuration

// lib/auth0.ts
import { Auth0Client } from "@auth0/nextjs-auth0/server";

export const auth0 = new Auth0Client();

Required environment variables:

AUTH0_SECRET=<random-secret>
AUTH0_BASE_URL=http://localhost:3000
AUTH0_ISSUER_BASE_URL=https://your-tenant.auth0.com
AUTH0_CLIENT_ID=<client-id>
AUTH0_CLIENT_SECRET=<client-secret>

Middleware

// middleware.ts
import { auth0 } from "@/lib/auth0";
import { NextRequest, NextResponse } from "next/server";

export async function middleware(request: NextRequest) {
  return await auth0.middleware(request);
}

export const config = {
  matcher: [
    "/((?!_next/static|_next/image|favicon.ico|sitemap.xml|robots.txt).*)",
  ],
};

Access Session Data

// Server component
import { auth0 } from "@/lib/auth0";

export default async function Page() {
  const session = await auth0.getSession();
  return session ? (
    <p>Hello, {session.user.name}</p>
  ) : (
    <a href="/auth/login">Log in</a>
  );
}

Decision Matrix

Need	Recommended	Why
Fastest setup on Vercel	Clerk	Native Marketplace, auto-provisioned env vars
Passwordless / social login flows	Descope	Visual flow builder, Marketplace native
Enterprise SSO / SAML / multi-tenant	Auth0	Deep enterprise identity support
Pre-built UI components	Clerk	Drop-in `<SignIn />`, `<UserButton />`
Vercel unified billing	Clerk or Descope	Both are native Marketplace integrations

Clerk Core 3 Breaking Changes (March 2026)

Clerk provides an upgrade CLI that scans your codebase and applies codemods: npx @clerk/upgrade. Requires Node.js 20.9.0+.

auth() is async — always use const { userId } = await auth(), not synchronous
auth.protect() moved — use await auth.protect() directly, not from the return value of auth()
clerkClient() is async — use await clerkClient() in middleware handlers
authMiddleware() removed — migrate to clerkMiddleware()
@clerk/types deprecated — import types from SDK subpath exports: import type { UserResource } from '@clerk/react/types' (works from any SDK package)
ClerkProvider no longer forces dynamic rendering — pass the dynamic prop if needed
Cache components — when using Next.js cache components, place <ClerkProvider> inside <body>, not wrapping <html>
Satellite domains — new satelliteAutoSync option skips handshake redirects when no session cookies exist
Smaller bundles — React is now shared across framework SDKs (~50KB gzipped savings)
Better offline handling — getToken() now correctly distinguishes signed-out from offline states

Cross-References

Marketplace install and env var provisioning → ⤳ skill: marketplace
Middleware routing patterns → ⤳ skill: routing-middleware
Environment variable management → ⤳ skill: env-vars

Official Documentation

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