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Node JS – Initialize Firebase using service account key or Firebase config file?

April 3, 2023

I’m trying to learn how to use Firebase with Node JS and there’s a thing I can’t understand. I’ve been looking for an explanation for a few days now, but I just can’t find something useful.

After following some tutorials, I’m confused because some of them use the serviceAccountKey file which looks like

    "type": "service_account",
    "project_id": 
    "private_key_id": 
    "private_key":
    "client_id": 
    "auth_uri": 
    "token_uri": 
    "auth_provider_x509_cert_url": 
    "client_x509_cert_url":

and then they initialize it like this

admin.initializeApp({
    credential: admin.credential.cert(credentials)
});

While others use the Firebase configuration file which is generated when you register the app on Firebase, which looks like this:

const firebaseConfig = {
  apiKey: 
  authDomain:
  projectId:
  storageBucket:
  messagingSenderId: 
  appId:
  measurementId:
}

What is the difference? When are you supposed to use the first way or the second way?
If there is some documentation about this, please help me with it because I can’t find anything relevant.