In Firebase’s case you will probably be on the free tier (as long as you are not guzzling data) up to 100k users . Think about this for a moment. You will have 100k users on your app. Even if you only add advertising you should be able to make the $25 a month to cover the Firebase FLAME costs.
Read moreIs Firebase email Auth free?
Auth is free . Firebase Authentication service is free in all plans.
Read moreIs Firebase phone Auth free?
All other Firebase Auth features are free to use on all plans .
Read moreHow do I get Firebase Auth?
Get Started with Firebase Authentication on Websites
Read moreWhat is Firebase Auth?
Firebase Authentication provides backend services, easy-to-use SDKs, and ready-made UI libraries to authenticate users to your app . It supports authentication using passwords, phone numbers, popular federated identity providers like Google, Facebook and Twitter, and more.
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