The Ultimate Guide to Web3 Authentication With Wagmi and NextAuth

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Web3 is transforming how users interact with digital platforms, shifting control from centralized entities to individuals through blockchain technology. At the heart of this transformation lies Web3 authentication—a secure, decentralized method that allows users to log in using their crypto wallets instead of traditional credentials. This guide explores how to implement Sign-In with Ethereum (SIWE) in a Next.js application using powerful tools like WAGMI, viem, NextAuth, Iron Session, and RainbowKit.

Whether you're building a decentralized finance (DeFi) platform, NFT marketplace, or blockchain-based social network, robust authentication is essential. Let’s dive into the core concepts, setup process, and integration workflow.

What Is Web3 Authentication?

Web3 authentication enables users to verify their identity using blockchain wallet signatures rather than usernames and passwords. When a user connects their wallet—such as MetaMask or WalletConnect—they sign a cryptographic message proving ownership of the wallet address.

This approach eliminates password fatigue, reduces phishing risks, and enhances privacy. Unlike traditional systems where user data is stored on centralized servers, Web3 authentication keeps control in the hands of users.

👉 Discover how modern authentication boosts security and user trust in decentralized apps.

Why Sign-In with Ethereum (SIWE) Matters

Sign-In with Ethereum (SIWE) is emerging as the gold standard for Web3 login systems. It provides a standardized way for users to authenticate across dApps using their Ethereum-signed messages.

SIWE works by generating a unique message containing:

The user signs this message with their private key. The server then verifies the signature and nonce to confirm authenticity. This process ensures:

For developers, SIWE offers a clean, audited, and interoperable solution that integrates seamlessly with modern frameworks.

Key Tools for Building SIWE Authentication

Let’s examine the core libraries powering this implementation:

WAGMI

A React Hooks library for Ethereum that simplifies wallet connections, transactions, and signing operations. Built on top of viem, it delivers type-safe, efficient Web3 interactions.

viem

A lightweight, tree-shakable TypeScript library for interacting with Ethereum nodes. It supports signing messages, reading contract data, and more—all without bloating your bundle.

SIWE

The official JavaScript/TypeScript library for implementing Sign-In with Ethereum. It handles message creation, parsing, and verification according to EIP-4361.

Iron Session

A minimal yet secure session management tool for Next.js. It encrypts session data server-side and stores it in cookies—perfect for maintaining state without a database.

NextAuth

A full-featured authentication framework for Next.js supporting OAuth, email/password, and custom credentials—including wallet-based logins.

RainbowKit

A React library that enhances wallet onboarding with beautiful UI components and built-in support for popular wallets.

Together, these tools form a modern, modular stack for building secure Web3 experiences.

Setting Up Your Next.js Project

Start by creating a new Next.js app:

pnpm create next-app web3-auth
cd web3-auth
pnpm install wagmi [email protected] @tanstack/react-query next-auth iron-session @rainbow-me/rainbowkit

Ensure you're using pnpm, though npm or yarn work equally well.

Next, configure environment variables:

SECRET=your_long_secure_secret_key_here

This secret encrypts sessions and should be kept confidential in production.

Implementing SIWE Authentication

Step 1: Configure React Query

WAGMI relies on React Query for state management:

import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
import { ReactNode, useState } from "react";

export default function ReactQueryProvider({ children }: { children: ReactNode }) {
  const [queryClient] = useState(() => new QueryClient());
  return <QueryClientProvider client={queryClient}>{children}</QueryClientProvider>;
}

Step 2: Set Up Auth Provider

Wrap your app with NextAuth’s SessionProvider:

"use client";
import { SessionProvider } from "next-auth/react";
import { ReactNode } from "react";

export default function AuthProvider({ children, session }: { children: ReactNode; session: any }) {
  return <SessionProvider session={session}>{children}</SessionProvider>;
}

Step 3: Integrate RainbowKit

Use RainbowKit to enable smooth wallet connection flows:

"use client";
import { WagmiProvider } from "wagmi";
import { RainbowKitProvider, RainbowKitAuthenticationProvider } from "@rainbow-me/rainbowkit";
import { config } from "@/config";
import { authenticationAdapter } from "@/utils/authenticationAdapter";

export default function RainbowKitWrapper({ children, cookie }: { children: ReactNode; cookie: string }) {
  const initialState = cookieToInitialState(config, cookie);

  return (
    <WagmiProvider config={config} initialState={initialState}>
      <QueryClientProvider>
        <RainbowKitAuthenticationProvider adapter={authenticationAdapter}>
          <RainbowKitProvider>{children}</RainbowKitProvider>
        </RainbowKitAuthenticationProvider>
      </QueryClientProvider>
    </WagmiProvider>
  );
}

👉 See how seamless wallet login improves conversion rates in real-world dApps.

Managing Sessions with Iron Session

To securely store nonces server-side, use Iron Session:

import { IronSessionOptions } from "iron-session";

export const sessionOptions: IronSessionOptions = {
  password: process.env.SESSION_PASSWORD!,
  cookieName: "siwe-session",
  cookieOptions: {
    secure: process.env.NODE_ENV === "production",
    httpOnly: true,
  },
};

Generate and store a nonce when requested:

export async function POST() {
  const nonce = generateNonce();
  await submitCookieToStorageServerAction(nonce);
  return NextResponse.json({ nonce }, { status: 201 });
}

Verifying Signatures with NextAuth

In authConfig.ts, define a credentials provider that validates SIWE messages:

authorize: async (credentials) => {
  const siwe = new SiweMessage(credentials!.message);
  const expectedNonce = await readCookieFromStorageServerAction();

  if (expectedNonce !== siwe.nonce) throw new Error("Invalid nonce");

  const result = await siwe.verify({ signature: credentials!.signature });
  if (result.success) {
    return { id: siwe.address, walletAddress: siwe.address };
  }
  return null;
}

Upon successful verification, NextAuth creates a session including the wallet address.

Securing API Routes

Protect backend endpoints by checking session status:

import { getServerSession } from "next-auth";

export async function GET() {
  const session = await getServerSession(authConfig);
  if (!session) return new Response("Unauthorized", { status: 401 });
  return new Response("Secure content");
}

Frequently Asked Questions

Q: Can SIWE work with non-Ethereum blockchains?
A: Yes. While named “Sign-In with Ethereum,” SIWE supports EVM-compatible chains like Polygon, Arbitrum, and BNB Smart Chain via chain ID specification.

Q: Is user data stored during SIWE login?
A: No personal data is collected unless explicitly added. Only the wallet address and signature are used for verification.

Q: How do I prevent replay attacks?
A: Always use a unique nonce per session attempt and invalidate it after use. Iron Session helps manage this securely.

Q: Can I combine SIWE with email login?
A: Absolutely. NextAuth allows multiple providers—including SIWE and Google/OAuth—enabling hybrid authentication models.

Q: Do users need ETH to sign in?
A: No. Signing messages is gas-free. Users only need a connected wallet and internet access.

Q: What happens if the nonce expires?
A: The user must request a new login challenge. Typical expiration is 5–10 minutes for security.

Final Thoughts

Implementing SIWE authentication using WAGMI, NextAuth, and RainbowKit delivers a secure, user-friendly login experience tailored for Web3. By leveraging industry-standard tools and protocols, you future-proof your dApp while maintaining high usability.

As decentralized identity evolves, early adoption of SIWE positions your project at the forefront of innovation.

👉 Start integrating advanced Web3 auth today—unlock better security and engagement.