[Home](./index.md) > [@firebase/auth](./auth.md) > [signInWithPhoneNumber](./auth.signinwithphonenumber.md)
## signInWithPhoneNumber() function
Asynchronously signs in using a phone number.
Signature:
```typescript
export declare function signInWithPhoneNumber(auth: Auth, phoneNumber: string, appVerifier: ApplicationVerifier): Promise;
```
## Parameters
| Parameter | Type | Description |
| --- | --- | --- |
| auth | [Auth](./auth.auth.md) | The Auth instance. |
| phoneNumber | string | The user's phone number in E.164 format (e.g. +16505550101). |
| appVerifier | [ApplicationVerifier](./auth.applicationverifier.md) | The [ApplicationVerifier](./auth.applicationverifier.md). |
Returns:
Promise<[ConfirmationResult](./auth.confirmationresult.md)>
## Remarks
This method sends a code via SMS to the given phone number, and returns a [ConfirmationResult](./auth.confirmationresult.md). After the user provides the code sent to their phone, call [ConfirmationResult.confirm()](./auth.confirmationresult.confirm.md) with the code to sign the user in.
For abuse prevention, this method also requires a [ApplicationVerifier](./auth.applicationverifier.md). This SDK includes a reCAPTCHA-based implementation, [RecaptchaVerifier](./auth.recaptchaverifier.md).
## Example
```javascript
// 'recaptcha-container' is the ID of an element in the DOM.
const applicationVerifier = new firebase.auth.RecaptchaVerifier('recaptcha-container');
const confirmationResult = await signInWithPhoneNumber(auth, phoneNumber, applicationVerifier);
// Obtain a verificationCode from the user.
const credential = await confirmationResult.confirm(verificationCode);
```