@auth/core

This is the main entry point to the Auth.js library.

Based on the Request and Response Web standard APIs. Primarily used to implement framework-specific packages, but it can also be used directly.

Installation

npm install @auth/core

pnpm add @auth/core

yarn add @auth/core

bun add @auth/core

Usage

import { Auth } from "@auth/core"
 
const request = new Request("https://example.com")
const response = await Auth(request, {...})
 
console.log(response instanceof Response) // true

Resources

• Getting started
• Guides

AuthConfig

Configure the Auth method.

Example

import Auth, { type AuthConfig } from "@auth/core"
 
export const authConfig: AuthConfig = {...}
 
const request = new Request("https://example.com")
const response = await AuthHandler(request, authConfig)

See

Initialization

Extended by

Properties

adapter?

optional adapter: Adapter;

You can use the adapter option to pass in your database adapter.

basePath?

optional basePath: string;

The base path of the Auth.js API endpoints.

Default

"/api/auth" in "next-auth"; "/auth" with all other frameworks

callbacks?

optional callbacks: {
  jwt: (params) => Awaitable<null | JWT>;
  redirect: (params) => Awaitable<string>;
  session: (params) => Awaitable<Session | DefaultSession>;
  signIn: (params) => Awaitable<string | boolean>;
};

Callbacks are asynchronous functions you can use to control what happens when an action is performed. Callbacks are extremely powerful, especially in scenarios involving JSON Web Tokens as they allow you to implement access controls without a database and to integrate with external databases or APIs.

jwt()?

optional jwt: (params) => Awaitable<null | JWT>;

This callback is called whenever a JSON Web Token is created (i.e. at sign in) or updated (i.e whenever a session is accessed in the client). Anything you return here will be saved in the JWT and forwarded to the session callback. There you can control what should be returned to the client. Anything else will be kept from your frontend. The JWT is encrypted by default via your AUTH_SECRET environment variable.

session callback

Parameters

Returns

Awaitable<null | JWT>

redirect()?

optional redirect: (params) => Awaitable<string>;

This callback is called anytime the user is redirected to a callback URL (i.e. on signin or signout). By default only URLs on the same host as the origin are allowed. You can use this callback to customise that behaviour.

Documentation

Example

callbacks: {
  async redirect({ url, baseUrl }) {
    // Allows relative callback URLs
    if (url.startsWith("/")) return `${baseUrl}${url}`
 
    // Allows callback URLs on the same origin
    if (new URL(url).origin === baseUrl) return url
 
    return baseUrl
  }
}

Parameters

Returns

Awaitable<string>

session()?

optional session: (params) => Awaitable<Session | DefaultSession>;

This callback is called whenever a session is checked. (i.e. when invoking the /api/session endpoint, using useSession or getSession). The return value will be exposed to the client, so be careful what you return here! If you want to make anything available to the client which you’ve added to the token through the JWT callback, you have to explicitly return it here as well.

The token argument is only available when using the jwt session strategy, and the user argument is only available when using the database session strategy.

jwt callback

Example

callbacks: {
  async session({ session, token, user }) {
    // Send properties to the client, like an access_token from a provider.
    session.accessToken = token.accessToken
 
    return session
  }
}

Parameters

Returns

Awaitable<Session | DefaultSession>

signIn()?

optional signIn: (params) => Awaitable<string | boolean>;

Controls whether a user is allowed to sign in or not. Returning true continues the sign-in flow. Returning false or throwing an error will stop the sign-in flow and redirect the user to the error page. Returning a string will redirect the user to the specified URL.

Unhandled errors will throw an AccessDenied with the message set to the original error.

AccessDenied

Example

callbacks: {
 async signIn({ profile }) {
  // Only allow sign in for users with email addresses ending with "yourdomain.com"
  return profile?.email?.endsWith("@yourdomain.com")
}

Parameters

Returns

Awaitable<string | boolean>

cookies?

optional cookies: Partial<CookiesOptions>;

You can override the default cookie names and options for any of the cookies used by Auth.js. You can specify one or more cookies with custom properties and missing options will use the default values defined by Auth.js. If you use this feature, you will likely want to create conditional behavior to support setting different cookies policies in development and production builds, as you will be opting out of the built-in dynamic policy.

• ⚠ This is an advanced option. Advanced options are passed the same way as basic options, but may have complex implications or side effects. You should try to avoid using advanced options unless you are very comfortable using them.

Default

{}

debug?

optional debug: boolean;

Set debug to true to enable debug messages for authentication and database operations.

• ⚠ If you added a custom AuthConfig.logger, this setting is ignored.

Default

false

events?

optional events: {
  createUser: (message) => Awaitable<void>;
  linkAccount: (message) => Awaitable<void>;
  session: (message) => Awaitable<void>;
  signIn: (message) => Awaitable<void>;
  signOut: (message) => Awaitable<void>;
  updateUser: (message) => Awaitable<void>;
};

Events are asynchronous functions that do not return a response, they are useful for audit logging. You can specify a handler for any of these events below - e.g. for debugging or to create an audit log. The content of the message object varies depending on the flow (e.g. OAuth or Email authentication flow, JWT or database sessions, etc), but typically contains a user object and/or contents of the JSON Web Token and other information relevant to the event.

Default

{}

createUser()?

optional createUser: (message) => Awaitable<void>;

Parameters

Returns

Awaitable<void>

linkAccount()?

optional linkAccount: (message) => Awaitable<void>;

Parameters

Returns

Awaitable<void>

session()?

optional session: (message) => Awaitable<void>;

The message object will contain one of these depending on if you use JWT or database persisted sessions:

• token: The JWT for this session.
• session: The session object from your adapter.

Parameters

Returns

Awaitable<void>

signIn()?

optional signIn: (message) => Awaitable<void>;

If using a credentials type auth, the user is the raw response from your credential provider. For other providers, you’ll get the User object from your adapter, the account, and an indicator if the user was new to your Adapter.

Parameters

Returns

Awaitable<void>

signOut()?

optional signOut: (message) => Awaitable<void>;

The message object will contain one of these depending on if you use JWT or database persisted sessions:

• token: The JWT for this session.
• session: The session object from your adapter that is being ended.

Parameters

Returns

Awaitable<void>

updateUser()?

optional updateUser: (message) => Awaitable<void>;

Parameters

Returns

Awaitable<void>

experimental?

optional experimental: {
  enableWebAuthn: boolean;
};

Use this option to enable experimental features. When enabled, it will print a warning message to the console.

Note

Experimental features are not guaranteed to be stable and may change or be removed without notice. Please use with caution.

Default

{}

enableWebAuthn?

optional enableWebAuthn: boolean;

Enable WebAuthn support.

Default

false

jwt?

optional jwt: Partial<JWTOptions>;

JSON Web Tokens are enabled by default if you have not specified an AuthConfig.adapter. JSON Web Tokens are encrypted (JWE) by default. We recommend you keep this behaviour.

logger?

optional logger: Partial<LoggerInstance>;

Override any of the logger levels (undefined levels will use the built-in logger), and intercept logs in NextAuth. You can use this option to send NextAuth logs to a third-party logging service.

Example

// /auth.ts
import log from "logging-service"
 
export const { handlers, auth, signIn, signOut } = NextAuth({
  logger: {
    error(code, ...message) {
      log.error(code, message)
    },
    warn(code, ...message) {
      log.warn(code, message)
    },
    debug(code, ...message) {
      log.debug(code, message)
    }
  }
})

• ⚠ When set, the AuthConfig.debug option is ignored

Default

console

pages?

optional pages: Partial<PagesOptions>;

Specify URLs to be used if you want to create custom sign in, sign out and error pages. Pages specified will override the corresponding built-in page.

Default

{}

Example

  pages: {
    signIn: '/auth/signin',
    signOut: '/auth/signout',
    error: '/auth/error',
    verifyRequest: '/auth/verify-request',
    newUser: '/auth/new-user'
  }

providers

providers: Provider[];

List of authentication providers for signing in (e.g. Google, Facebook, Twitter, GitHub, Email, etc) in any order. This can be one of the built-in providers or an object with a custom provider.

Default

[]

raw?

optional raw: typeof raw;

redirectProxyUrl?

optional redirectProxyUrl: string;

When set, during an OAuth sign-in flow, the redirect_uri of the authorization request will be set based on this value.

This is useful if your OAuth Provider only supports a single redirect_uri or you want to use OAuth on preview URLs (like Vercel), where you don’t know the final deployment URL beforehand.

The url needs to include the full path up to where Auth.js is initialized.

Note

This will auto-enable the state OAuth2Config.checks on the provider.

Example

"https://authjs.example.com/api/auth"

You can also override this individually for each provider.

Example

GitHub({
  ...
  redirectProxyUrl: "https://github.example.com/api/auth"
})

Default

AUTH_REDIRECT_PROXY_URL environment variable

See also: Guide: Securing a Preview Deployment

secret?

optional secret: string | string[];

A random string used to hash tokens, sign cookies and generate cryptographic keys.

To generate a random string, you can use the Auth.js CLI: npx auth secret

Note

You can also pass an array of secrets, in which case the first secret that successfully decrypts the JWT will be used. This is useful for rotating secrets without invalidating existing sessions. The newer secret should be added to the start of the array, which will be used for all new sessions.

session?

optional session: {
  generateSessionToken: () => string;
  maxAge: number;
  strategy: "jwt" | "database";
  updateAge: number;
};

Configure your session like if you want to use JWT or a database, how long until an idle session expires, or to throttle write operations in case you are using a database.

generateSessionToken()?

optional generateSessionToken: () => string;

Generate a custom session token for database-based sessions. By default, a random UUID or string is generated depending on the Node.js version. However, you can specify your own custom string (such as CUID) to be used.

Default

randomUUID or randomBytes.toHex depending on the Node.js version

Returns

string

maxAge?

optional maxAge: number;

Relative time from now in seconds when to expire the session

Default

2592000 // 30 days

strategy?

optional strategy: "jwt" | "database";

Choose how you want to save the user session. The default is "jwt", an encrypted JWT (JWE) in the session cookie.

If you use an adapter however, we default it to "database" instead. You can still force a JWT session by explicitly defining "jwt".

When using "database", the session cookie will only contain a sessionToken value, which is used to look up the session in the database.

Documentation | Adapter | About JSON Web Tokens

updateAge?

optional updateAge: number;

How often the session should be updated in seconds. If set to 0, session is updated every time.

Default

86400 // 1 day

skipCSRFCheck?

optional skipCSRFCheck: typeof skipCSRFCheck;

theme?

optional theme: Theme;

Changes the theme of built-in AuthConfig.pages.

trustHost?

optional trustHost: boolean;

Auth.js relies on the incoming request’s host header to function correctly. For this reason this property needs to be set to true.

Make sure that your deployment platform sets the host header safely.

useSecureCookies?

optional useSecureCookies: boolean;

When set to true then all cookies set by NextAuth.js will only be accessible from HTTPS URLs. This option defaults to false on URLs that start with http:// (e.g. http://localhost:3000) for developer convenience. You can manually set this option to false to disable this security feature and allow cookies to be accessible from non-secured URLs (this is not recommended).

• ⚠ This is an advanced option. Advanced options are passed the same way as basic options, but may have complex implications or side effects. You should try to avoid using advanced options unless you are very comfortable using them.

The default is false HTTP and true for HTTPS sites.

customFetch

const customFetch: typeof customFetch;

It can be used to support corporate proxies, custom fetch libraries, cache discovery endpoints, add mocks for testing, logging, set custom headers/params for non-spec compliant providers, etc.

Example

import { Auth, customFetch } from "@auth/core"
import GitHub from "@auth/core/providers/github"
 
const dispatcher = new ProxyAgent("my.proxy.server")
function proxy(...args: Parameters<typeof fetch>): ReturnType<typeof fetch> {
  return undici(args[0], { ...(args[1] ?? {}), dispatcher })
}
 
const response = await Auth(request, {
  providers: [GitHub({ [customFetch]: proxy })]
})

See

• https://undici.nodejs.org/#/docs/api/ProxyAgent?id=example-basic-proxy-request-with-local-agent-dispatcher
• https://authjs.dev/guides/corporate-proxy

raw

const raw: typeof raw;

Auth.js returns a web standard Response by default, but if you are implementing a framework you might want to get access to the raw internal response by passing this value to AuthConfig.raw.

skipCSRFCheck

const skipCSRFCheck: typeof skipCSRFCheck;

Auth.js comes with built-in CSRF protection, but if you are implementing a framework that is already protected against CSRF attacks, you can skip this check by passing this value to AuthConfig.skipCSRFCheck.

Auth()

Auth(request, config)

Auth(request, config): Promise<ResponseInternal>

Core functionality provided by Auth.js.

Receives a standard Request and returns a Response.

Parameters

Returns

Promise<ResponseInternal>

Example

import { Auth } from "@auth/core"
 
const request = new Request("https://example.com")
const response = await Auth(request, {
  providers: [Google],
  secret: "...",
  trustHost: true,
})

See

Documentation

Auth(request, config)

Auth(request, config): Promise<Response>

Core functionality provided by Auth.js.

Receives a standard Request and returns a Response.

Parameters

Returns

Promise<Response>

Example

import { Auth } from "@auth/core"
 
const request = new Request("https://example.com")
const response = await Auth(request, {
  providers: [Google],
  secret: "...",
  trustHost: true,
})

See

Documentation

createActionURL()

createActionURL(
   action, 
   protocol, 
   headers, 
   envObject, 
   config): URL

Parameters

Returns

URL

isAuthAction()

isAuthAction(action): action is AuthAction

Parameters

Returns

action is AuthAction

setEnvDefaults()

setEnvDefaults(
   envObject, 
   config, 
   suppressBasePathWarning): void

Set default env variables on the config object

Parameters

Returns

void