Why Firebase private key needed?

[KeisukeNagakawa]

Hi, I’m new to NextJS, and I am struggling to understand why private key for Firebase is needed in this project.

When using Firebase in react(not NextJS), all I need to use Firebase service in the client side is just a public key(and set of other info too but not private key).

But, this project requires private key in .env file. I don’t see the necessities for it…why?

I wish someone is kind enough to teach me the necessity for it. Thank you.

[kmjennison]

It's used to verify the user's ID token on the server side, which allows your app to use the user's ID during server-side rendering and in API functions. Verifying the ID token requires the Firebase admin app.