Email/password authentication in Supabase

Introduction

Email/password authentication lets users sign up and log in using their email and a password. It keeps accounts safe and easy to use.

You want users to create accounts with their email and password.

You need to control who can access your app or service.

You want a simple way to manage user sign-in without social logins.

You want to send password reset emails to users.

You want to protect user data behind a login.

Syntax

Supabase

const { data, error } = await supabase.auth.signUp({
  email: '[e-mail]',
  password: 'strong-password'
})

Use signUp to register a new user with email and password.

Check error to handle signup problems like weak passwords or duplicate emails.

Examples

Registers a new user with email [e-mail] and password password123.

Supabase

const { data, error } = await supabase.auth.signUp({
  email: '[e-mail]',
  password: 'password123'
})

Logs in an existing user with email and password.

Supabase

const { data, error } = await supabase.auth.signInWithPassword({
  email: '[e-mail]',
  password: 'password123'
})

Attempts signup with a weak password; error will explain the issue.

Supabase

const { data, error } = await supabase.auth.signUp({
  email: '[e-mail]',
  password: 'weak'
})

Sample Program

This code creates a Supabase client and registers a new user with email and password. It prints success or error messages.

Supabase

import { createClient } from '@supabase/supabase-js'

const supabaseUrl = 'https://xyzcompany.supabase.co'
const supabaseKey = 'public-anonymous-key'
const supabase = createClient(supabaseUrl, supabaseKey)

async function registerUser() {
  const { data, error } = await supabase.auth.signUp({
    email: '[e-mail]',
    password: 'SecurePass123!'
  })

  if (error) {
    console.log('Signup error:', error.message)
  } else {
    console.log('Signup success! User ID:', data.user.id)
  }
}

registerUser()

Important Notes

Passwords should be strong to keep accounts safe.

Supabase sends a confirmation email by default after signup.

Always handle errors to improve user experience.

Summary

Email/password authentication lets users create and access accounts securely.

Use signUp to register and signInWithPassword to log in.

Check for errors to handle weak passwords or duplicate emails.

Practice

1. What is the primary purpose of using signUp in Supabase email/password authentication?

easy

A. To register a new user with email and password

B. To log in an existing user

C. To reset a user's password

D. To delete a user account

Solution

1. Step 1: Understand the function of signUp

   The signUp method is used to create a new user account with an email and password.

2. Step 2: Differentiate from other authentication methods

   Logging in uses signInWithPassword, not signUp. Password reset and deletion are separate actions.

3. Final Answer:

   To register a new user with email and password -> Option A

4. Quick Check:

   signUp = register new user [OK]

Hint: Remember: signUp means create account, not login [OK]

Common Mistakes:

• Confusing signUp with signInWithPassword
• Thinking signUp resets passwords
• Assuming signUp deletes accounts

2. Which of the following is the correct syntax to sign in a user with email and password using Supabase?

easy

A. supabase.auth.login({ email: '[e-mail]', password: 'pass123' })

B. supabase.auth.signInWithPassword({ email: '[e-mail]', password: 'pass123' })

C. supabase.auth.signUp({ email: '[e-mail]', password: 'pass123' })

D. supabase.auth.authenticate({ email: '[e-mail]', password: 'pass123' })

Solution

1. Step 1: Identify the correct method for signing in

   The method to sign in with email and password is signInWithPassword.

2. Step 2: Check the syntax format

   The correct syntax uses an object with email and password keys inside signInWithPassword.

3. Final Answer:

   supabase.auth.signInWithPassword({ email: '[e-mail]', password: 'pass123' }) -> Option B

4. Quick Check:

   signInWithPassword = login syntax [OK]

Hint: signInWithPassword is for login, signUp is for registration [OK]

Common Mistakes:

• Using signUp instead of signInWithPassword to login
• Using non-existent methods like login or authenticate
• Incorrect object structure in method call

3. What will be the result of this code snippet?

const { data, error } = await supabase.auth.signUp({ email: '[e-mail]', password: '123' });
console.log(error ? error.message : 'User created');

medium

A. Password should be at least 6 characters

B. User created

C. Email already exists

D. SyntaxError

Solution

1. Step 1: Analyze the password length

   The password '123' is only 3 characters, which is too short for Supabase's minimum password length (usually 6).

2. Step 2: Understand error handling

   The error object will contain a message about the weak password, so the console logs that message.

3. Final Answer:

   Password should be at least 6 characters -> Option A

4. Quick Check:

   Short password triggers error message [OK]

Hint: Passwords must meet minimum length to avoid errors [OK]

Common Mistakes:

• Assuming user is created with short password
• Ignoring error object and expecting success
• Confusing error messages for duplicate email

4. You wrote this code to sign in a user:

const { data, error } = await supabase.auth.signInWithPassword({ email: '[e-mail]' });

Why does it fail and how to fix it?

medium

A. Use signUp instead of signInWithPassword

B. Email format is wrong; fix the email string

C. Missing password field; add password to the object

D. signInWithPassword requires a callback function

Solution

1. Step 1: Check required parameters for signInWithPassword

   The method requires both email and password fields to authenticate.

2. Step 2: Identify missing password

   The code only provides email, so it fails. Adding password fixes the issue.

3. Final Answer:

   Missing password field; add password to the object -> Option C

4. Quick Check:

   Both email and password needed for signInWithPassword [OK]

Hint: Always provide both email and password to signInWithPassword [OK]

Common Mistakes:

• Omitting password when signing in
• Confusing signUp and signInWithPassword usage
• Thinking signInWithPassword needs a callback

5. You want to create a secure signup flow that prevents duplicate emails and weak passwords. Which approach is best?

hard

A. Call signInWithPassword first, then signUp if login fails

B. Allow signup without email verification to speed up user creation

C. Only check password length on client side, skip server validation

D. Use signUp and check error for duplicates or weak passwords before confirming success

Solution

1. Step 1: Use signUp to register users

   This method handles creating accounts and returns errors for duplicates or weak passwords.

2. Step 2: Check the error object to handle issues

   By checking error, you can inform users about duplicates or weak passwords and prevent bad signups.

3. Final Answer:

   Use signUp and check error for duplicates or weak passwords before confirming success -> Option D

4. Quick Check:

   signUp + error check = secure signup flow [OK]

Hint: Always check errors after signUp to catch duplicates and weak passwords [OK]

Common Mistakes:

• Trying to sign in before signup to check duplicates
• Skipping server-side password validation
• Ignoring email verification importance