To sign in users by SMS, you must first enable the Phone Number sign-in method for your Firebase project:
- In the Firebase console, open the Authentication section.
- On the Sign-in Method page, enable the Phone Number sign-in method.
Firebase's phone number sign-in request quota is high enough that most apps won't be affected. However, if you need to sign in a very high volume of users with phone authentication, you might need to upgrade your pricing plan. See the pricing page.
To get an API key:
- Visit the Google Cloud Platform Console.
- Click the project drop-down and select or create the project for which you want to add an API key.
- Click the menu button and select APIs & Services > Credentials.
- On the Credentials page, click Create credentials > API key. The API key created dialog displays your newly created API key.
- Click Close. The new API key is listed on the Credentials page under API keys.
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