Better Auth Integration

Overview

Better Auth works well with @capgo/capacitor-social-login when you want native sign-in on the device but still want Better Auth to create and manage the session on your backend.

This page focuses on the two integration patterns that fit best:

• Native token handoff for Google, Apple, and Facebook
• Better Auth Generic OAuth for providers like Auth0, Okta, Keycloak, and custom OIDC servers

Which pattern to use

Use native token handoff

Use SocialLogin.login() first, then send the returned token to Better Auth with authClient.signIn.social() when you use:

• Google
• Apple
• Facebook

Use Better Auth Generic OAuth

Let Better Auth own the full OAuth redirect flow when you use:

• Auth0
• Okta
• Keycloak
• GitHub
• OneLogin
• Any custom OAuth2 or OIDC provider

That keeps the session exchange on the Better Auth side and avoids duplicating redirect logic between two systems.

Better Auth server setup

Start by configuring Better Auth with the social providers you want to support:

import { betterAuth } from 'better-auth';

export const auth = betterAuth({
  baseURL: process.env.BETTER_AUTH_URL,
  socialProviders: {
    google: {
      clientId: process.env.GOOGLE_CLIENT_ID as string,
      clientSecret: process.env.GOOGLE_CLIENT_SECRET as string,
    },
    apple: {
      clientId: process.env.APPLE_CLIENT_ID as string,
      clientSecret: process.env.APPLE_CLIENT_SECRET as string,
      appBundleIdentifier: process.env.APPLE_APP_BUNDLE_IDENTIFIER as string,
    },
    facebook: {
      clientId: process.env.FACEBOOK_CLIENT_ID as string,
      clientSecret: process.env.FACEBOOK_CLIENT_SECRET as string,
    },
  },
  trustedOrigins: ['https://appleid.apple.com'],
});

Note

For Apple on native iOS, Better Auth documents that you should provide appBundleIdentifier so the Apple ID token audience matches the bundle identifier used by iOS.

Better Auth client setup

import { createAuthClient } from 'better-auth/client';

export const authClient = createAuthClient({
  baseURL: 'https://auth.example.com',
});

If you use React, use the Better Auth React client package your app already uses. The token handoff pattern stays the same.

Google example

This is the cleanest integration path for native mobile Google sign-in:

import { SocialLogin } from '@capgo/capacitor-social-login';
import { authClient } from '@/lib/auth-client';

const googleResult = await SocialLogin.login({
  provider: 'google',
  options: {
    scopes: ['profile', 'email'],
  },
});

if (googleResult.result.responseType !== 'online' || !googleResult.result.idToken) {
  throw new Error('Google online mode with idToken is required for Better Auth.');
}

await authClient.signIn.social({
  provider: 'google',
  idToken: {
    token: googleResult.result.idToken,
    accessToken: googleResult.result.accessToken?.token,
  },
  callbackURL: '/dashboard',
});

Apple example

For Apple, pass the same nonce to both the native login request and Better Auth:

import { SocialLogin } from '@capgo/capacitor-social-login';
import { authClient } from '@/lib/auth-client';

const nonce = crypto.randomUUID();

const appleResult = await SocialLogin.login({
  provider: 'apple',
  options: {
    scopes: ['email', 'name'],
    nonce,
  },
});

if (!appleResult.result.idToken) {
  throw new Error('Apple idToken is required for Better Auth.');
}

await authClient.signIn.social({
  provider: 'apple',
  idToken: {
    token: appleResult.result.idToken,
    nonce,
    accessToken: appleResult.result.accessToken?.token,
  },
  callbackURL: '/dashboard',
});

Facebook example

Better Auth documents two Facebook handoff modes:

• iOS Limited Login: pass the idToken
• Access-token flow: pass the access token as both token and accessToken

This works with the response shape from @capgo/capacitor-social-login:

import { SocialLogin } from '@capgo/capacitor-social-login';
import { authClient } from '@/lib/auth-client';

const facebookResult = await SocialLogin.login({
  provider: 'facebook',
  options: {
    permissions: ['email', 'public_profile'],
  },
});

const betterAuthToken = facebookResult.result.idToken
  ? {
      token: facebookResult.result.idToken,
    }
  : facebookResult.result.accessToken?.token
    ? {
        token: facebookResult.result.accessToken.token,
        accessToken: facebookResult.result.accessToken.token,
      }
    : null;

if (!betterAuthToken) {
  throw new Error('Facebook idToken or access token is required for Better Auth.');
}

await authClient.signIn.social({
  provider: 'facebook',
  idToken: betterAuthToken,
  callbackURL: '/dashboard',
});

Generic OAuth providers with Better Auth

For Auth0, Okta, Keycloak, GitHub, Microsoft Entra ID, and similar providers, Better Auth’s Generic OAuth plugin is usually the better fit than passing tokens from SocialLogin.login({ provider: 'oauth2' }).

Better Auth server

import { betterAuth } from 'better-auth';
import { genericOAuth } from 'better-auth/plugins';

export const auth = betterAuth({
  plugins: [
    genericOAuth({
      config: [
        {
          providerId: 'keycloak',
          discoveryUrl: 'https://sso.example.com/realms/mobile/.well-known/openid-configuration',
          clientId: process.env.KEYCLOAK_CLIENT_ID as string,
          clientSecret: process.env.KEYCLOAK_CLIENT_SECRET as string,
        },
      ],
    }),
  ],
});

Better Auth client

import { createAuthClient } from 'better-auth/client';
import { genericOAuthClient } from 'better-auth/client/plugins';

export const authClient = createAuthClient({
  baseURL: 'https://auth.example.com',
  plugins: [genericOAuthClient()],
});

await authClient.signIn.oauth2({
  providerId: 'keycloak',
  callbackURL: '/dashboard',
});

Provider examples for Better Auth Generic OAuth

Better Auth ships pre-configured helpers for several providers. These are the closest match to the extra provider examples you see in the social-login plugin docs.

Auth0

import { betterAuth } from 'better-auth';
import { auth0, genericOAuth } from 'better-auth/plugins';

export const auth = betterAuth({
  plugins: [
    genericOAuth({
      config: [
        auth0({
          providerId: 'auth0',
          domain: 'dev-example.eu.auth0.com',
          clientId: process.env.AUTH0_CLIENT_ID as string,
          clientSecret: process.env.AUTH0_CLIENT_SECRET as string,
          scopes: ['openid', 'profile', 'email', 'offline_access'],
        }),
      ],
    }),
  ],
});

await authClient.signIn.oauth2({
  providerId: 'auth0',
  callbackURL: '/dashboard',
});

Microsoft Entra ID

import { betterAuth } from 'better-auth';
import { genericOAuth, microsoftEntraId } from 'better-auth/plugins';

export const auth = betterAuth({
  plugins: [
    genericOAuth({
      config: [
        microsoftEntraId({
          providerId: 'entra',
          tenantId: 'common',
          clientId: process.env.AZURE_CLIENT_ID as string,
          clientSecret: process.env.AZURE_CLIENT_SECRET as string,
          scopes: ['openid', 'profile', 'email', 'User.Read'],
        }),
      ],
    }),
  ],
});

await authClient.signIn.oauth2({
  providerId: 'entra',
  callbackURL: '/dashboard',
});

Okta

import { betterAuth } from 'better-auth';
import { genericOAuth, okta } from 'better-auth/plugins';

export const auth = betterAuth({
  plugins: [
    genericOAuth({
      config: [
        okta({
          providerId: 'okta',
          issuer: 'https://dev-12345.okta.com/oauth2/default',
          clientId: process.env.OKTA_CLIENT_ID as string,
          clientSecret: process.env.OKTA_CLIENT_SECRET as string,
          scopes: ['openid', 'profile', 'email', 'offline_access'],
        }),
      ],
    }),
  ],
});

await authClient.signIn.oauth2({
  providerId: 'okta',
  callbackURL: '/dashboard',
});

Keycloak

import { betterAuth } from 'better-auth';
import { genericOAuth, keycloak } from 'better-auth/plugins';

export const auth = betterAuth({
  plugins: [
    genericOAuth({
      config: [
        keycloak({
          providerId: 'keycloak',
          issuer: 'https://sso.example.com/realms/mobile',
          clientId: process.env.KEYCLOAK_CLIENT_ID as string,
          clientSecret: process.env.KEYCLOAK_CLIENT_SECRET as string,
          scopes: ['openid', 'profile', 'email', 'offline_access'],
        }),
      ],
    }),
  ],
});

await authClient.signIn.oauth2({
  providerId: 'keycloak',
  callbackURL: '/dashboard',
});

GitHub with manual Generic OAuth config

GitHub does not have a Better Auth helper on the Generic OAuth page, so use manual configuration:

import { betterAuth } from 'better-auth';
import { genericOAuth } from 'better-auth/plugins';

export const auth = betterAuth({
  plugins: [
    genericOAuth({
      config: [
        {
          providerId: 'github',
          clientId: process.env.GITHUB_CLIENT_ID as string,
          clientSecret: process.env.GITHUB_CLIENT_SECRET as string,
          authorizationUrl: 'https://github.com/login/oauth/authorize',
          tokenUrl: 'https://github.com/login/oauth/access_token',
          userInfoUrl: 'https://api.github.com/user',
          scopes: ['read:user', 'user:email'],
          pkce: true,
        },
      ],
    }),
  ],
});

await authClient.signIn.oauth2({
  providerId: 'github',
  callbackURL: '/dashboard',
});

Notes and caveats

1. Use Google online mode Better Auth needs the idToken, so google.mode: 'offline' is not the right fit for this handoff flow.

2. Reuse the Apple nonce Generate it once, send it to Apple native login, then send the same value to Better Auth.

3. Handle Facebook differently by platform Limited Login on iOS gives you an ID token. Other flows may only give an access token.

4. Do not mix Generic OAuth flows unless you have a reason If Better Auth owns the OAuth provider configuration, let Better Auth own the redirect flow too.

Further reading

• Better Auth Google provider docs
• Better Auth Apple provider docs
• Better Auth Facebook provider docs
• Better Auth Generic OAuth plugin docs
• Social Login OAuth2 and OIDC providers