[Home](./index.md) > [@firebase/auth](./auth.md) > [signInWithPopup](./auth.signinwithpopup.md)
## signInWithPopup() function
Authenticates a Firebase client using a popup-based OAuth authentication flow.
Signature:
```typescript
export declare function signInWithPopup(auth: Auth, provider: AuthProvider, resolver?: PopupRedirectResolver): Promise;
```
## Parameters
| Parameter | Type | Description |
| --- | --- | --- |
| auth | [Auth](./auth.auth.md) | The Auth instance. |
| provider | [AuthProvider](./auth.authprovider.md) | The provider to authenticate. The provider has to be an [OAuthProvider](./auth.oauthprovider.md). Non-OAuth providers like [EmailAuthProvider](./auth.emailauthprovider.md) will throw an error. |
| resolver | [PopupRedirectResolver](./auth.popupredirectresolver.md) | An instance of [PopupRedirectResolver](./auth.popupredirectresolver.md), optional if already supplied to [initializeAuth()](./auth.initializeauth.md) or provided by [getAuth()](./auth.getauth.md). |
Returns:
Promise<[UserCredential](./auth.usercredential.md)>
## Remarks
If succeeds, returns the signed in user along with the provider's credential. If sign in was unsuccessful, returns an error object containing additional information about the error.
## Example
```javascript
// Sign in using a popup.
const provider = new FacebookAuthProvider();
const result = await signInWithPopup(auth, provider);
// The signed-in user info.
const user = result.user;
// This gives you a Facebook Access Token.
const credential = provider.credentialFromResult(auth, result);
const token = credential.accessToken;
```