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Integrating Third Party Backends

Integrating with third-party backends

When logging in through a provider, you can use the received OAuth tokens to authenticate against a third-party API. These tokens can be used to authorize requests to backends that are supporting the corresponding provider.

For example:

  • GitHub’s access_token will give you access to GitHub’s APIs.
  • Self-managed providers (like Keycloak) can be used to authorize against custom third-party backends.

Storing the token in the session

The token(s) are made availale in the account parameter of the jwt callback. To store them in the session, they can be attached to the token first.

jwt({ token, trigger, session, account }) {
  if (account?.provider === "my-provider") {
    return { ...token, accessToken: account.access_token }
  // ...

In order to access the token when making API requests, it needs to be made available to the Auth.js session.

async session({ session, token }) {
  session.accessToken = token.accessToken
  return session

Using the token to make authorized API requests

OAuth tokens are commonly attached as Authorization: Bearer <> header. It is recommended to attach this header server side, like a Route Handler.

export async function handler(request: NextRequest) {
  const session = await auth()
  return await fetch(/*<your-backend-url>/api/authenticated/greeting*/, {
    headers: { "Authorization":  `Bearer ${session?.accessToken}` }
  // ...

Configuring the backend to authorize requests through your provider

Consult your backend framework’s documentation on how to verify incoming access tokens. Below is an example with Express.js using a Keycloak instance.

const app = express()
const jwtCheck = jwt({
  secret: jwks.expressJwtSecret({
    cache: true,
    rateLimit: true,
    jwksRequestsPerMinute: 5,
  issuer: "",
  algorithms: ["RS256"],
app.get("*", jwtCheck, (req, res) => {
  const name = req.auth?.name ?? "unknown name"
  res.json({ greeting: `Hello, ${name}!` })
// ...


  • Further examples for different backend frameworks can be found here.
  • A full example of how to integrate a client app with a third-party API can be found in the next-auth-example.
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