[Home](./index.md) > [@firebase/auth](./auth.md) > [MultiFactorResolver](./auth.multifactorresolver.md) > [resolveSignIn](./auth.multifactorresolver.resolvesignin.md) ## MultiFactorResolver.resolveSignIn() method A helper function to help users complete sign in with a second factor using an [MultiFactorAssertion](./auth.multifactorassertion.md) confirming the user successfully completed the second factor challenge. Signature: ```typescript resolveSignIn(assertion: MultiFactorAssertion): Promise; ``` ## Parameters | Parameter | Type | Description | | --- | --- | --- | | assertion | [MultiFactorAssertion](./auth.multifactorassertion.md) | The multi-factor assertion to resolve sign-in with. | Returns: Promise<[UserCredential](./auth.usercredential.md)> The promise that resolves with the user credential object. ## Example ```javascript const phoneAuthCredential = PhoneAuthProvider.credential(verificationId, verificationCode); const multiFactorAssertion = PhoneMultiFactorGenerator.assertion(phoneAuthCredential); const userCredential = await resolver.resolveSignIn(multiFactorAssertion); ```