# Firebase Auth - Phone

To be able to use OTP service in your apps, you need to first enable Phone auth service in your firebase project.

### Enable phone authentication on firebase first.

1. Click on **authentication**
2. Click on **Sign-in method** tab
3.  click on **phone** then enable it\
    \


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### **Authorized Backend To Communicate with firebase**

1. Move the **settings** tab, scroll to the **Authorized domains**
2. Click on **Add Domain** to add your backend url to the list of authorized domains
3.  Add your **backend domain**. This is so firebase can allow request from your server.\


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