Fix Auth Redirects in V0 Apps | Quick Fix

TL;DR

Redirect issues in V0 authentication flows are caused by OAuth callback URL mismatches, infinite redirect loops between login and protected pages, and incorrect redirect targets after sign-in. Fix these by ensuring the callback URL in your auth provider matches your Vercel deployment domain exactly, using Next.js middleware for route protection instead of client-side redirects, and storing the intended destination before redirecting to login so users return to the correct page after authentication.

Why authentication redirects break in V0 deployments

Authentication flows involve multiple redirects: the user visits a protected page, gets redirected to login, authenticates with an external provider, and gets redirected back. Each redirect must point to the correct URL. In V0 projects, these break for several reasons. The OAuth callback URL configured in the auth provider (Supabase, Firebase, Google) points to the V0 preview URL but the app is deployed to a different Vercel domain. Client-side redirect logic creates infinite loops when the auth state is not yet available during server-side rendering. And the middleware redirect target does not account for the user's original destination, sending everyone to the homepage after login instead of where they wanted to go.

OAuth callback URL in the auth provider console does not match the deployed Vercel domain
Client-side auth check in a useEffect redirects before the session has loaded, causing an infinite loop
Next.js middleware redirects to /login, which also triggers the middleware, creating a loop
The V0 preview URL (*.v0.app) is configured as the callback but the production URL is different
Missing redirect URL parameter that tracks where the user was trying to go before being sent to login

Error messages you might see

Error: redirect_uri_mismatch — The redirect_uri in the request did not match a registered redirect_uri

The OAuth provider (Google, GitHub) received a callback URL that does not match any URL registered in the provider's console. Add your Vercel deployment URL to the authorized redirect URIs.

ERR_TOO_MANY_REDIRECTS — This page isn't working. [domain] redirected you too many times.

A redirect loop exists between two pages. Commonly, the middleware redirects to /login, and the login page's auth check redirects back to the protected page because the session exists but has not been verified yet.

Error: Invalid URL in redirect — The redirect URL 'undefined' is not valid.

The redirect target URL is undefined or null. This happens when environment variables for the callback URL are not set in the Vercel deployment or the Vars panel.

Before you start

A V0 project with authentication and protected routes
Access to the auth provider console (Supabase Dashboard, Firebase Console, or Google Cloud Console)
The production Vercel deployment URL

How to fix it

Update OAuth callback URLs to match your deployment domain

OAuth providers only redirect to URLs that are explicitly registered in their console. When you deploy from V0 to Vercel, the domain changes and the callback URL must be updated.

Update OAuth callback URLs to match your deployment domain

OAuth providers only redirect to URLs that are explicitly registered in their console. When you deploy from V0 to Vercel, the domain changes and the callback URL must be updated.

Open your auth provider's console. For Supabase: Dashboard > Authentication > URL Configuration. For Firebase: Console > Authentication > Settings > Authorized domains. For Google OAuth: Google Cloud Console > Credentials > OAuth 2.0 Client IDs. Add your Vercel deployment URL as an authorized redirect URI.

Before

typescript

// Supabase URL Configuration — only V0 preview URL
// Site URL: https://your-project.v0.app
// Redirect URLs: https://your-project.v0.app/auth/callback

After

typescript

// Supabase URL Configuration — includes production URL
// Site URL: https://your-app.vercel.app
// Redirect URLs:
//   https://your-app.vercel.app/auth/callback
//   https://your-project.v0.app/auth/callback  (keep for dev)
//   http://localhost:3000/auth/callback  (keep for local dev)

Expected result: OAuth redirects work on both the V0 preview and the production Vercel deployment.

Fix middleware redirect loops by excluding the login page

If your middleware redirects unauthenticated users to /login but also runs on the /login route, it creates an infinite loop. The login page must be excluded from auth protection.

Fix middleware redirect loops by excluding the login page

If your middleware redirects unauthenticated users to /login but also runs on the /login route, it creates an infinite loop. The login page must be excluded from auth protection.

Update the middleware matcher configuration to exclude the login page, public pages, and static assets from the auth check.

Before

typescript

// middleware.ts — runs on ALL routes including /login
export async function middleware(request: NextRequest) {
  const session = await getSession(request);
  if (!session) {
    return NextResponse.redirect(new URL("/login", request.url));
  }
}
export const config = {
  matcher: ["/(.*)"],
};

After

typescript

// middleware.ts — excludes login and public routes
import { createServerClient } from "@supabase/ssr";
import { NextResponse, type NextRequest } from "next/server";
export async function middleware(request: NextRequest) {
  let response = NextResponse.next({ request });
  const supabase = createServerClient(
    process.env.NEXT_PUBLIC_SUPABASE_URL!,
    process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!,
    {
      cookies: {
        getAll() { return request.cookies.getAll(); },
        setAll(cookies) {
          cookies.forEach(({ name, value, options }) =>
            response.cookies.set(name, value, options)
          );
        },
      },
    }
  );
  const { data: { user } } = await supabase.auth.getUser();
  if (!user) {
    const loginUrl = new URL("/login", request.url);
    loginUrl.searchParams.set("redirect", request.nextUrl.pathname);
    return NextResponse.redirect(loginUrl);
  }
  return response;
}
export const config = {
  matcher: ["/dashboard/:path*", "/settings/:path*", "/account/:path*"],
};

Expected result: Unauthenticated users are redirected to /login without a loop, and the original URL is preserved as a query parameter.

Redirect users to their intended destination after login

After authentication, users should return to the page they originally tried to visit, not always the homepage. The redirect parameter from the middleware stores the original URL.

Redirect users to their intended destination after login

After authentication, users should return to the page they originally tried to visit, not always the homepage. The redirect parameter from the middleware stores the original URL.

In the login page component, read the redirect parameter from the URL. After successful authentication, redirect to that URL instead of a hardcoded path.

Before

typescript

"use client";
export function LoginForm() {
  const handleLogin = async () => {
    await supabase.auth.signInWithPassword({ email, password });
    // Always redirects to home — loses the original destination
    window.location.href = "/";
  };
}

After

typescript

"use client";
import { useSearchParams, useRouter } from "next/navigation";
export function LoginForm() {
  const searchParams = useSearchParams();
  const router = useRouter();
  const redirectTo = searchParams.get("redirect") || "/dashboard";
  const handleLogin = async () => {
    const { error } = await supabase.auth.signInWithPassword({
      email,
      password,
    });
    if (!error) {
      router.push(redirectTo);
    }
  };
}

Expected result: After login, users return to the page they were trying to visit instead of always landing on the homepage.

Create the OAuth callback route handler

OAuth flows redirect to a callback URL after the user authenticates with the external provider. This route must exchange the authorization code for a session and redirect the user to their destination.

Create the OAuth callback route handler

Create an API route at app/auth/callback/route.ts that handles the OAuth code exchange and redirects the user.

Before

typescript

// No callback handler — OAuth redirect goes to 404

After

typescript

// app/auth/callback/route.ts
import { createServerClient } from "@supabase/ssr";
import { cookies } from "next/headers";
import { NextResponse } from "next/server";
export async function GET(request: Request) {
  const { searchParams, origin } = new URL(request.url);
  const code = searchParams.get("code");
  const redirect = searchParams.get("redirect") || "/dashboard";
  if (code) {
    const cookieStore = await cookies();
    const supabase = createServerClient(
      process.env.NEXT_PUBLIC_SUPABASE_URL!,
      process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!,
      {
        cookies: {
          getAll() { return cookieStore.getAll(); },
          setAll(cookies) {
            cookies.forEach(({ name, value, options }) =>
              cookieStore.set(name, value, options)
            );
          },
        },
      }
    );
    await supabase.auth.exchangeCodeForSession(code);
  }
  return NextResponse.redirect(new URL(redirect, origin));
}

Expected result: OAuth callback exchanges the code for a session and redirects the user to their intended destination.

Complete code example

middleware.ts

1import { createServerClient } from "@supabase/ssr";
2import { NextResponse, type NextRequest } from "next/server";
3
4export async function middleware(request: NextRequest) {
5  let response = NextResponse.next({ request });
6
7  const supabase = createServerClient(
8    process.env.NEXT_PUBLIC_SUPABASE_URL!,
9    process.env.NEXT_PUBLIC_SUPABASE_ANON_KEY!,
10    {
11      cookies: {
12        getAll() {
13          return request.cookies.getAll();
14        },
15        setAll(cookiesToSet) {
16          cookiesToSet.forEach(({ name, value, options }) => {
17            response.cookies.set(name, value, options);
18          });
19        },
20      },
21    }
22  );
23
24  const {
25    data: { user },
26  } = await supabase.auth.getUser();
27
28  if (!user) {
29    const loginUrl = new URL("/login", request.url);
30    loginUrl.searchParams.set("redirect", request.nextUrl.pathname);
31    return NextResponse.redirect(loginUrl);
32  }
33
34  return response;
35}
36
37export const config = {
38  matcher: [
39    "/dashboard/:path*",
40    "/settings/:path*",
41    "/account/:path*",
42  ],
43};

Best practices to prevent this

Add all deployment URLs (V0 preview, Vercel production, localhost) as authorized redirect URIs in your auth provider
Exclude login, signup, and public pages from middleware auth checks to prevent redirect loops
Store the user's intended destination as a URL parameter before redirecting to login
Use server-side middleware for route protection instead of client-side useEffect redirects to avoid flash of protected content
Create a dedicated /auth/callback route handler for OAuth code exchange
For complex auth flows with multiple providers and role-based redirects, RapidDev can design and implement the complete auth architecture

Still stuck?

Copy one of these prompts to get a personalized, step-by-step explanation.

ChatGPT Prompt

My V0 Next.js app has a redirect loop after login. The middleware sends users to /login, and after signing in they get redirected back to /login again instead of /dashboard. How do I fix the redirect loop and preserve the user's intended destination?

Frequently asked questions

Why do I get a redirect_uri_mismatch error after deploying my V0 app?

The OAuth callback URL registered in your auth provider still points to the V0 preview URL. Update the authorized redirect URIs in your provider's console to include your Vercel deployment domain (e.g., https://your-app.vercel.app/auth/callback).

How do I fix an infinite redirect loop between login and dashboard?

Ensure your middleware matcher does not include the /login route. If the middleware checks auth on /login, it finds no session and redirects to /login again, creating an infinite loop. Use the matcher config to specify only protected routes.

How do I redirect users back to their original page after login?

In the middleware, append the original URL as a query parameter when redirecting to /login (e.g., /login?redirect=/dashboard/settings). In the login form, read this parameter with useSearchParams and redirect to it after successful authentication.

Should I use middleware or useEffect for route protection?

Use middleware. It runs before the page renders, so unauthenticated users never see a flash of protected content. Client-side useEffect checks run after rendering, showing the protected page briefly before redirecting.

Can RapidDev help fix complex authentication redirect issues?

Yes. RapidDev can debug and fix redirect loops, configure OAuth callback URLs across multiple environments, implement role-based redirects, and set up a complete auth flow that works seamlessly between V0 preview and production deployments.

Do I need separate callback URLs for development and production?

Yes. Add all environment URLs as authorized redirect URIs: http://localhost:3000/auth/callback for local development, your V0 preview URL, and your Vercel production URL. This ensures OAuth works in every environment.

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Resolving redirect issues in V0 authentication flows

Why authentication redirects break in V0 deployments

Error messages you might see

Before you start

How to fix it

Update OAuth callback URLs to match your deployment domain

Update OAuth callback URLs to match your deployment domain

Fix middleware redirect loops by excluding the login page

Fix middleware redirect loops by excluding the login page

Redirect users to their intended destination after login

Redirect users to their intended destination after login

Create the OAuth callback route handler

Create the OAuth callback route handler

Complete code example

Best practices to prevent this

Still stuck?

Frequently asked questions

Talk to an Expert

Need help with your Lovable project?

We put the rapid in RapidDev

Resolving redirect issues in V0 authentication flows

Why authentication redirects break in V0 deployments

Error messages you might see

Before you start

How to fix it

Update OAuth callback URLs to match your deployment domain

Update OAuth callback URLs to match your deployment domain

Fix middleware redirect loops by excluding the login page

Fix middleware redirect loops by excluding the login page

Redirect users to their intended destination after login

Redirect users to their intended destination after login

Create the OAuth callback route handler

Create the OAuth callback route handler

Complete code example

Best practices to prevent this

Still stuck?

Related error patterns

Adding OAuth providers (Google, GitHub) to v0 apps

Fixing token expiration issues in v0 auth flows

Integrating Firebase or Supabase authentication with v0

Explore related guides

Frequently asked questions

Talk to an Expert

Need help with your Lovable project?

We put the rapid in RapidDev