Sign in with Base

Implement Base Account authentication using the proper SIWE flow with Wagmi

Learn how to implement Sign in with Base using Wagmi by accessing the Base Account provider and following the proper SIWE (Sign-In With Ethereum) authentication flow.

Prerequisites

Make sure you have set up Wagmi with Base Account before following this guide.

Overview

To implement Sign in with Base with Wagmi, you need to:

1. Get the Base Account connector from Wagmi
2. Access the underlying provider from the connector
3. Use wallet_connect with signInWithEthereum capabilities
4. Verify the signature on your backend

This follows the same flow as shown in the authenticate users guide, but integrates with Wagmi’s connector system.

Implementation

Code Snippets

Browser (Wagmi + SDK)

import { useState } from 'react'
import { useConnect, useAccount, useDisconnect } from 'wagmi'
import { baseAccount } from 'wagmi/connectors'

export function SignInWithBase() {
  const [isLoading, setIsLoading] = useState(false)
  const [error, setError] = useState<string | null>(null)
  const { isConnected, address } = useAccount()
  const { connectAsync, connectors } = useConnect()
  const { disconnect } = useDisconnect()

  // Find the Base Account connector
  const baseAccountConnector = connectors.find(
    connector => connector.id === 'baseAccountWallet'
  )

  const handleSignIn = async () => {
    if (!baseAccountConnector) {
      setError('Base Account connector not found')
      return
    }

    setIsLoading(true)
    setError(null)

    try {
      // 1 — get a fresh nonce (generate locally or prefetch from backend)
      const nonce = window.crypto.randomUUID().replace(/-/g, '')
      // OR prefetch from server
      // const nonce = await fetch('/auth/nonce').then(r => r.text())

      // 2 — connect and get the provider
      await connectAsync({ connector: baseAccountConnector })
      const provider = baseAccountConnector.provider

      // 3 — authenticate with wallet_connect
      const authResult = await provider.request({
        method: 'wallet_connect',
        params: [{
          version: '1',
          capabilities: {
            signInWithEthereum: { 
              nonce, 
              chainId: '0x2105' // Base Mainnet - 8453
            }
          }
        }]
      })

      const { accounts } = authResult
      const { address, capabilities } = accounts[0]
      const { message, signature } = capabilities.signInWithEthereum

      // 4 — verify on backend
      await fetch('/auth/verify', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ address, message, signature })
      })
    } catch (err: any) {
      console.error(`err ${err}`)
      setError(err.message || 'Sign in failed')
    } finally {
      setIsLoading(false)
    }
  }

  if (isConnected) {
    return (
      <div className="flex items-center gap-4">
        <span className="font-mono text-sm">{address}</span>
        <button onClick={() => disconnect()}>Sign Out</button>
      </div>
    )
  }

  return (
    <button onClick={handleSignIn} disabled={isLoading}>
      {isLoading ? 'Signing in...' : 'Sign in with Base'}
    </button>
  )
}

3. Using the Pre-built Button Component

You can also use the official Sign In With Base button component:

// components/SignInButton.tsx
import { SignInWithBaseButton } from '@base-org/account-ui/react'
import { useConnect } from 'wagmi'

export function SignInButton() {
  const { connectAsync, connectors } = useConnect()

  const handleSignIn = async () => {
    const baseAccountConnector = connectors.find(
      connector => connector.id === 'baseAccountWallet'
    )

    if (!baseAccountConnector) return

    try {
      // Generate nonce
      const nonce = window.crypto.randomUUID().replace(/-/g, '')

      // Connect and get provider
      await connectAsync({ connector: baseAccountConnector })
      const provider = baseAccountConnector.provider

      // Perform SIWE authentication
      const authResult = await provider.request({
        method: 'wallet_connect',
        params: [{
          version: '1',
          capabilities: {
            signInWithEthereum: { 
              nonce, 
              chainId: '0x2105'
            }
          }
        }]
      })

      // Extract and verify signature
      const { accounts } = authResult
      const { address, capabilities } = accounts[0]
      const { message, signature } = capabilities.signInWithEthereum

      // Send to backend for verification
      await fetch('/auth/verify', {
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ address, message, signature })
      })
    } catch (error) {
      console.error('Authentication failed:', error)
    }
  }

  return (
    <SignInWithBaseButton
      colorScheme="light"
      onClick={handleSignIn}
    />
  )
}

Please Follow the Brand Guidelines

If you intend on using the SignInWithBaseButton, please follow the Brand Guidelines to ensure consistency across your application.