Firebase Alternative ?

Firebase is not an easy thing to replace, it's a whole suite of tools that include things like authentication, real time database, serverless functions and sdk's that can easily tie this infrastructure together on iOS, Android and web.
let's compare Firebase and Supabase to see how they differ.

Services

Supabase currently offers Database, Authentication, Storage and Functions. There are a lot of features missing from Supabase, like static site hosting, machine learning tools, push notification service and google analytics, so firebase has more features.

Database

Supabase is a relational database, while Firebase is a NoSQL database. Both database types have their pros and cons. For instance, NoSQL databases are popular for search engines and social media feeds.
Choosing the right database for your app depends on what type of app you're building.

Authentication

Authentication with Supabase is same as with Firebase. Your dashboard has all the data about your users and email templates.
The sign-in methods include email and password as well as all major OAuth providers. only the phone authentication is missing which you can find in Firebase.

Pricing

both of them have a base free tier, which is only useful for experimentation.
When you build something serious on firebase, you use the pay-as-you-go plan, each individual service has a free tier, so that you only pay for what you use. Supabase has 8GB database storage and 100K users for $25 a month. in firebase you also pay for the number of reads and writes to the database but in Supabase it looks like you have unlimited api calls and network traffic to your database.

Conclusion

Supabase only has a JavaScript SDK, on the other hand Firebase is extremely popular with mobile developers and you couldn't really call supabase an alternative to firebase until they release an SDK for iOS and Android.