Authentication providers overview in Firebase - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is an authentication provider in Firebase?

An authentication provider in Firebase is a service that allows users to sign in to your app using different methods like email/password, social accounts, or phone numbers.

beginner

Name three common Firebase authentication providers.

Three common Firebase authentication providers are Email/Password, Google Sign-In, and Phone Authentication.

intermediate

How does Google Sign-In work as a Firebase authentication provider?

Google Sign-In lets users log in using their Google account. Firebase handles the connection securely and provides your app with the user's identity.

intermediate

What is the benefit of using multiple authentication providers in Firebase?

Using multiple providers lets users choose how they want to sign in, improving user experience and making your app accessible to more people.

intermediate

What is anonymous authentication in Firebase?

Anonymous authentication lets users access your app without signing up. Later, they can link their anonymous account to a permanent provider like email or Google.

Which Firebase authentication provider allows users to sign in with their phone number?

A Email/Password

B Google Sign-In

C Phone Authentication

D Anonymous Authentication

Phone Authentication lets users sign in using their phone number and a verification code.

What does Firebase provide after a user signs in with an authentication provider?

A User identity and credentials

B User's password

C User's email only

D User's device information

Firebase provides the user's identity and credentials securely to your app after sign-in.

Which authentication provider is best if you want users to sign in without creating an account first?

A Facebook Login

B Anonymous Authentication

C Google Sign-In

D Email/Password

Anonymous Authentication allows users to use the app without signing up initially.

Which of these is NOT a Firebase authentication provider?

A Phone Authentication

B Email/Password

C Twitter Sign-In

D LinkedIn Sign-In

LinkedIn Sign-In is not a built-in Firebase authentication provider.

Why might you want to enable multiple authentication providers in your Firebase app?

A To give users more sign-in options

B To increase app size

C To make sign-in slower

D To limit user access

Multiple providers let users pick their preferred sign-in method, improving accessibility.

Explain the main types of authentication providers available in Firebase and when you might use each.

Think about different ways users can prove who they are.

Describe the benefits of supporting multiple authentication providers in a Firebase app.

Consider how users might want to sign in differently.

Practice

1. Which of the following is NOT a Firebase Authentication provider?

easy

A. Google

B. Twitter

C. LinkedIn

D. Facebook

Solution

1. Step 1: Recall Firebase supported providers

   Firebase supports Google, Facebook, Twitter, Email/Password, Phone, and Anonymous sign-in.

2. Step 2: Identify unsupported provider

   LinkedIn is not officially supported as a Firebase Authentication provider.

3. Final Answer:

   LinkedIn -> Option C

4. Quick Check:

   Firebase providers exclude LinkedIn [OK]

Hint: Remember common providers: Google, Facebook, Twitter, no LinkedIn [OK]

Common Mistakes:

• Confusing LinkedIn as supported
• Thinking all social logins are included
• Mixing OAuth providers with Firebase support

2. Which Firebase Authentication method is used to start a Google sign-in flow in JavaScript?

easy

A. firebase.auth().signInWithPopup(new firebase.auth.GoogleAuthProvider())

B. firebase.auth().signInWithGoogle()

C. firebase.auth().signInWithRedirect('google')

D. firebase.auth().signInWithEmailAndPassword('google')

Solution

1. Step 1: Identify correct method for Google sign-in

   Firebase uses signInWithPopup() or signInWithRedirect() with a provider instance.

2. Step 2: Match method and provider

   signInWithPopup(new firebase.auth.GoogleAuthProvider()) is the correct syntax to start Google sign-in.

3. Final Answer:

   firebase.auth().signInWithPopup(new firebase.auth.GoogleAuthProvider()) -> Option A

4. Quick Check:

   Use signInWithPopup with GoogleAuthProvider [OK]

Hint: Use signInWithPopup with new GoogleAuthProvider() [OK]

Common Mistakes:

• Using non-existent signInWithGoogle()
• Passing string instead of provider object
• Confusing email sign-in method

3. What will the following Firebase Authentication code do?

const provider = new firebase.auth.FacebookAuthProvider();
firebase.auth().signInWithPopup(provider).then(result => {
  console.log(result.user.email);
});

medium

A. Sign in anonymously and log user ID

B. Start Google sign-in and log user's email on success

C. Throw an error because FacebookAuthProvider is invalid

D. Start Facebook sign-in and log user's email on success

Solution

1. Step 1: Analyze provider and method

   The code creates a FacebookAuthProvider and calls signInWithPopup(provider), which starts Facebook sign-in.

2. Step 2: Understand the then() callback

   On success, it logs the signed-in user's email from result.user.email.

3. Final Answer:

   Start Facebook sign-in and log user's email on success -> Option D

4. Quick Check:

   FacebookAuthProvider + signInWithPopup logs email [OK]

Hint: Provider class matches sign-in method and logs user email [OK]

Common Mistakes:

• Confusing Facebook with Google provider
• Expecting anonymous sign-in
• Thinking provider is invalid

4. Identify the error in this Firebase Authentication code snippet for phone sign-in:

const provider = new firebase.auth.PhoneAuthProvider();
firebase.auth().signInWithPopup(provider).then(result => {
  console.log(result.user.phoneNumber);
});

medium

A. Missing email parameter for phone sign-in

B. PhoneAuthProvider cannot be used with signInWithPopup()

C. PhoneAuthProvider requires OAuth scopes

D. signInWithPopup() only works with anonymous sign-in

Solution

1. Step 1: Check usage of PhoneAuthProvider

   PhoneAuthProvider is used differently; it does not support signInWithPopup().

2. Step 2: Identify correct phone sign-in method

   Phone sign-in uses verification codes and confirmation, not popup OAuth flows.

3. Final Answer:

   PhoneAuthProvider cannot be used with signInWithPopup() -> Option B

4. Quick Check:

   Phone sign-in uses verification, not popup [OK]

Hint: Phone sign-in uses verification, not popup method [OK]

Common Mistakes:

• Trying to use popup with phone provider
• Expecting email for phone sign-in
• Confusing OAuth scopes with phone auth

5. You want to allow users to sign in anonymously but later link their account to Google sign-in. Which Firebase Authentication approach is correct?

hard

A. Use signInAnonymously() first, then linkWithPopup(new GoogleAuthProvider())

B. Use signInWithPopup(new GoogleAuthProvider()) only, no anonymous sign-in

C. Use signInAnonymously() only, no linking possible

D. Use signInWithEmailAndPassword() then linkWithPopup(new GoogleAuthProvider())

Solution

1. Step 1: Understand anonymous sign-in and linking

   Firebase allows anonymous sign-in, then linking that anonymous user to another provider.

2. Step 2: Identify correct linking method

   After signInAnonymously(), use linkWithPopup() with GoogleAuthProvider to link accounts.

3. Final Answer:

   Use signInAnonymously() first, then linkWithPopup(new GoogleAuthProvider()) -> Option A

4. Quick Check:

   Anonymous sign-in + linkWithPopup for Google [OK]

Hint: Sign in anonymously, then link Google with linkWithPopup() [OK]

Common Mistakes:

• Skipping linking step
• Using only Google sign-in without anonymous
• Trying to link email/password instead