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Supabasecloud~5 mins

Magic link authentication in Supabase - Cheat Sheet & Quick Revision

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Recall & Review
beginner
What is magic link authentication?
Magic link authentication is a way to sign in users by sending them a special link via email. Clicking the link logs them in without needing a password.
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beginner
How does magic link authentication improve user experience?
It removes the need to remember passwords, making login faster and simpler, like clicking a link in your email to get access.
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intermediate
What role does Supabase play in magic link authentication?
Supabase provides backend services that handle sending the magic link email and verifying the link when clicked, managing user sessions securely.
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intermediate
What is a key security benefit of magic link authentication?
Since no password is stored or entered, it reduces risks like password theft or reuse, making it safer for users.
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intermediate
What happens if a magic link expires or is used multiple times?
Magic links usually expire after a short time and can only be used once to prevent unauthorized access.
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What does a magic link do in authentication?
ALogs in a user by clicking a link sent to their email
BRequires a password to be entered
CSends a text message with a code
DUses fingerprint scanning
Which of these is a main advantage of magic link authentication?
AIt requires complex passwords
BIt uses biometric data
CUsers don’t need to remember passwords
DIt stores passwords on the device
In Supabase, what happens after a user clicks the magic link?
ASupabase verifies the link and logs the user in
BThe user must enter a password
CThe link redirects to a signup page
DThe user receives a phone call
Why do magic links expire?
ATo save email space
BTo prevent unauthorized reuse
CTo force users to change passwords
DTo slow down login
Which is NOT true about magic link authentication?
AIt allows passwordless login
BIt sends a login link via email
CIt improves security by avoiding password storage
DIt requires users to remember complex passwords
Explain how magic link authentication works in Supabase from sending the link to user login.
Think about the steps from email to login without passwords.
You got /5 concepts.
    Describe the security benefits and potential risks of using magic link authentication.
    Consider what makes it safer and what to watch out for.
    You got /5 concepts.

      Practice

      (1/5)
      1. What is the main purpose of magic link authentication in Supabase?
      easy
      A. Authenticate users using biometric data like fingerprints
      B. Require users to enter a password and a code sent via SMS
      C. Use social media accounts for login
      D. Allow users to log in by clicking a link sent to their email without using a password

      Solution

      1. Step 1: Understand magic link authentication

        Magic link authentication lets users log in by clicking a special link sent to their email, avoiding passwords.

      2. Step 2: Compare options with this definition

        Only Allow users to log in by clicking a link sent to their email without using a password describes login via email link without passwords, matching the magic link concept.

      3. Final Answer:

        Allow users to log in by clicking a link sent to their email without using a password -> Option D

      4. Quick Check:

        Magic link = login via email link without password [OK]
      Hint: Magic link means login by email link, no password needed [OK]
      Common Mistakes:
      • Confusing magic link with password or biometric login
      • Thinking magic link requires SMS codes
      • Assuming social login is magic link
      2. Which is the correct way to call Supabase's magic link sign-in method in JavaScript?
      easy
      A. supabase.auth.signInWithPassword({ email: 'user@example.com' })
      B. supabase.auth.signInWithOtp({ email: 'user@example.com' })
      C. supabase.auth.signInWithMagicLink('user@example.com')
      D. supabase.auth.loginWithOtp('user@example.com')

      Solution

      1. Step 1: Recall Supabase magic link method name

        The correct method is signInWithOtp with an object containing the email.

      2. Step 2: Match method and parameter format

        supabase.auth.signInWithOtp({ email: 'user@example.com' }) uses signInWithOtp with an object { email: '...' }, which is correct syntax.

      3. Final Answer:

        supabase.auth.signInWithOtp({ email: 'user@example.com' }) -> Option B

      4. Quick Check:

        Method name and parameter object = supabase.auth.signInWithOtp({ email: 'user@example.com' }) [OK]
      Hint: Use signInWithOtp with email in an object [OK]
      Common Mistakes:
      • Using wrong method names like signInWithPassword
      • Passing email as a string instead of an object
      • Confusing method names with social login
      3. What will the following code do?
      const { data, error } = await supabase.auth.signInWithOtp({ email: 'test@example.com' });
      console.log(data);
      console.log(error);
      medium
      A. Send a magic link to 'test@example.com' and log data with confirmation info, error null
      B. Return error because email format is invalid
      C. Throw a syntax error because signInWithOtp requires a password
      D. Send a magic link to 'test@example.com' and log data with user info, error null

      Solution

      1. Step 1: Understand signInWithOtp behavior

        This method sends a magic link to the email and returns data about the request, not user info immediately.

      2. Step 2: Analyze console output

        Data contains confirmation info about sending the link; error is null if successful. No syntax error or invalid email here.

      3. Final Answer:

        Send a magic link to 'test@example.com' and log data with confirmation info, error null -> Option A

      4. Quick Check:

        signInWithOtp sends link, returns confirmation data [OK]
      Hint: signInWithOtp returns confirmation data, not user info [OK]
      Common Mistakes:
      • Expecting immediate user info in data
      • Thinking password is required
      • Assuming invalid email error for valid format
      4. You wrote this code but users report they never receive magic links:
      await supabase.auth.signInWithOtp('user@example.com');

      What is the problem?
      medium
      A. The method name is incorrect, should be signInWithMagicLink
      B. Magic links require a password parameter
      C. The email should be passed inside an object, not as a string
      D. You must call a separate sendMagicLink function after signInWithOtp

      Solution

      1. Step 1: Check method parameter format

        signInWithOtp expects an object with an email property, not a plain string.

      2. Step 2: Identify why magic link is not sent

        Passing a string causes the method to fail silently or not send the email, so users get no link.

      3. Final Answer:

        The email should be passed inside an object, not as a string -> Option C

      4. Quick Check:

        Email must be in object for signInWithOtp [OK]
      Hint: Pass email as { email: '...' }, not just a string [OK]
      Common Mistakes:
      • Passing email as string instead of object
      • Thinking password is needed for magic link
      • Using wrong method names
      5. You want to implement magic link login but only allow users with emails from 'example.com'. Which approach is best?
      hard
      A. Before calling signInWithOtp, check if email ends with '@example.com' and reject others
      B. Call signInWithOtp for all emails, then filter users after login
      C. Use signInWithOtp and set a password for domain restriction
      D. Configure Supabase to block all emails except 'example.com' automatically

      Solution

      1. Step 1: Understand domain restriction needs

        To restrict login to a domain, validate the email before sending magic link.

      2. Step 2: Choose best practice

        Checking email domain in your app before calling signInWithOtp prevents sending links to unauthorized users.

      3. Final Answer:

        Before calling signInWithOtp, check if email ends with '@example.com' and reject others -> Option A

      4. Quick Check:

        Pre-check email domain before magic link send [OK]
      Hint: Validate email domain before sending magic link [OK]
      Common Mistakes:
      • Sending magic links to all emails then filtering
      • Thinking password is needed for domain restriction
      • Assuming Supabase blocks domains automatically
      Recommended

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