How to Use Cognito for Web Applications: Complete Step by Step Guide
By Braincuber Team
Published on March 27, 2026
AWS Cognito is a cloud-based, serverless solution for identity and access management that provides capabilities similar to Auth0 and Okta. As part of the AWS suite of services, it integrates seamlessly with other AWS services and offers a cost-effective way to handle user authentication in web applications.
What You'll Learn:
- Understanding OAuth 2.0 authentication flow
- Setting up Cognito User Pools and Application Clients
- Configuring hosted UI and authentication endpoints
- Implementing user registration and sign-in flows
- Securing server-side endpoints with JWT validation
- Managing users and administrative tasks
Solution Overview
This tutorial covers building a complete authentication system with the following components:
Simple React UI
User interface providing basic authentication functionality
Registration
Email verification and user sign-up process
Signing In
Secure authentication with OAuth 2.0 flow
Server-side Authentication
JWT token validation and secure endpoint protection
Logout
Secure session termination and cleanup
Key Concepts: OAuth 2.0
Before diving into Cognito, it's essential to understand OAuth 2.0, the standard that underpins modern authentication systems.
Step 1: Understanding OAuth 2.0
OAuth 2.0 is an Internet Standard (RFC 6749) implemented by many services including Auth0, Azure Active Directory, and Amazon Cognito. It provides security and convenience by allowing application owners to authenticate users without storing passwords.
Why Not Naïve Authentication?
Avoid storing passwords or password hashes in your database. This creates serious security risks and is not recommended unless absolutely necessary.
OAuth Benefits
- No password storage required
- Standardized authentication flow
- Support for multi-factor authentication
- Token-based security
Step 2: OAuth Authentication Flow
The OAuth 2.0 authentication flow consists of several key steps:
Redirect to Authorization UI
Redirect users from your app to the authorization server's login page
Login with Authorization Server
User provides credentials on the authorization server's hosted UI
Callback with Authorization Code
Server redirects back to your app with an authorization code
Exchange Code for Tokens
Trade the authorization code for ID, access, and refresh tokens
Verify Tokens
Validate JWT tokens using the authorization server's public keys
Token Types
- ID Token: Contains user identity information (name, email, phone)
- Access Token: Contains resource access permissions
- Refresh Token: Used to obtain new tokens without re-authentication
Step 3: Security Hardening with PKCE
Protect against redirect interception attacks using PKCE (Proof Key for Code Exchange):
Generate Code Verifier
Create a random string (code verifier) and store it client-side
Create Code Challenge
Generate SHA-256 hash of the code verifier
Include in Initial Request
Add code_challenge parameter to the authorization URL
Verify During Token Exchange
Include code verifier when exchanging authorization code for tokens
Cognito Concepts
Step 4: Create User Pools
User pools are essentially a database of users combined with sign-up and sign-in capabilities:
resource "aws_cognito_user_pool" "pool" {
name = var.user_pool_name
email_verification_subject = "Your verification code"
email_verification_message = "Your verification code is {####}."
schema {
attribute_data_type = "String"
name = "email"
required = true
mutable = true
string_attribute_constraints {
min_length = 1
max_length = 100
}
}
username_attributes = ["email"]
auto_verified_attributes = ["email"]
password_policy {
minimum_length = 6
require_lowercase = false
require_numbers = false
require_symbols = false
require_uppercase = false
}
device_configuration {
challenge_required_on_new_device = true
device_only_remembered_on_user_prompt = false
}
}Key Configuration
- Schema: Define user attributes (email is minimum recommended)
- Auto-verification: Automatically verify email addresses
- Password Policy: Set password requirements
- Device Configuration: Manage device tracking
Step 5: Configure Application Clients
Application clients define how your web or mobile applications interact with Cognito:
resource "aws_cognito_user_pool_client" "client" {
name = "${var.user_pool_name}-client"
user_pool_id = aws_cognito_user_pool.pool.id
callback_urls = [var.callback_url]
default_redirect_uri = var.callback_url
allowed_oauth_flows_user_pool_client = true
allowed_oauth_flows = ["code", "implicit"]
allowed_oauth_scopes = ["email", "openid"]
supported_identity_providers = ["COGNITO"]
}Client Configuration
- Callback URLs: Where users are redirected after authentication
- OAuth Flows: Enable authorization code and implicit flows
- Scopes: Define what information can be accessed
- Identity Providers: Configure login methods
Step 6: Set Up Hosted UI and Domain
Configure the hosted UI and custom domain for your authentication pages:
resource "aws_cognito_user_pool_domain" "main" {
domain = data.aws_acm_certificate.wildcard.domain
certificate_arn = aws_acm_certificate.wildcard.arn
user_pool_id = aws_cognito_user_pool.pool.id
}
resource "aws_cognito_user_pool_ui_customization" "ui" {
css = ".label-customizable {font-weight: 400;}"
image_file = filebase64("favicon-32x32.png")
user_pool_id = aws_cognito_user_pool_domain.main.user_pool_id
}UI Customization
- Custom Domain: Use your own domain for authentication pages
- SSL Certificate: Secure the authentication domain
- CSS Customization: Style the hosted UI to match your brand
- Logo/Branding: Add your company logo and colors
Authentication Endpoints
Step 7: Understand Cognito Endpoints
Cognito provides several key endpoints for authentication:
Sign In Endpoint
/oauth2/authorize - Default sign-in UI with sign-up and password recovery options
Sign Up Endpoint
/signup - Dedicated sign-up interface
Token Endpoint
/oauth2/token - Exchange authorization codes for tokens
Logout Endpoint
/logout - Force users to log out and clear sessions
URL Construction
Endpoints require proper parameterization with client ID, redirect URI, and PKCE values. Use libraries to construct correct URLs.
Implementation: User Authentication
Step 8: Implement User Sign-up and Sign-in
Implement the authentication flow in your web application:
import { getLoggedInUser, handleRedirectCallback, loginWithRedirect } from 'user-management';
const Index = (props: { message: string }): JSX.Element => {
const user = getLoggedInUser();
handleRedirectCallback();
return (
<>
{!user && (
)}
);
};getLoggedInUser()
Returns user identity and access tokens if logged in
handleRedirectCallback()
Processes OAuth callback and exchanges code for tokens
loginWithRedirect()
Redirects user to Cognito hosted UI for authentication
signUpWithRedirect()
Redirects to sign-up flow instead of sign-in
Step 9: Secure Server-side Endpoints
Validate JWT tokens on the server to secure your API endpoints:
import { connectWithCognito } from 'user-management';
export const handler: SSRHandler = async (event, context) => {
const cookies = getCookies((event.cookies || []).join(';'));
if (cookies.goldstack_access_token) {
const cognito = await connectWithCognito();
await cognito.validate(cookies.goldstack_access_token);
const idToken = await cognito.validateIdToken(cookies.goldstack_id_token);
message = `Hello ${idToken.email}
`;
}
};Critical Security Note
Always validate tokens using the validate() methods. Never decode tokens directly without validation, as this bypasses security checks.
Extract Tokens
Get tokens from cookies or Authorization headers
Validate Access Token
Verify token signature and expiration
Validate ID Token
Extract user information from validated ID token
Authorize Access
Grant access based on validated user identity
User Management
Step 10: Manage Users and Administrative Tasks
Use the AWS Console for user management tasks:
Access Cognito Console
Navigate to Cognito service in AWS Management Console
Select User Pool
Choose your user pool from the list
View Users and Groups
Go to General Settings > Users and Groups
Administrative Tasks
Reset passwords, disable users, export user lists
Important Note
Make configuration changes through Terraform files, not the AWS Console, to maintain infrastructure as code practices.
Best Practices:
- Infrastructure as Code: Use Terraform to manage Cognito configurations
- Token Validation: Always validate JWT tokens, never decode directly
- PKCE Implementation: Use PKCE for public client applications
- Minimal User Attributes: Only collect necessary user data
- Security Headers: Implement proper CORS and security headers
- Monitoring: Set up CloudWatch alarms for authentication failures
Frequently Asked Questions
What is AWS Cognito and how does it compare to Auth0 or Okta?
AWS Cognito is a cloud-based identity and access management service that provides similar capabilities to Auth0 and Okta. It's particularly advantageous if you're already using AWS services, offering seamless integration and cost-effective pricing. However, Auth0 and Okta may provide more flexibility and features for non-AWS environments.
What is the difference between authentication and authorization?
Authentication verifies who a user is (their identity), while authorization determines what they can access (their permissions). This tutorial focuses on authentication - validating that users are who they claim to be using AWS Cognito.
Why should I use OAuth 2.0 instead of storing passwords directly?
OAuth 2.0 eliminates the need to store passwords, reducing security risks and liability. It provides standardized authentication flows, supports multi-factor authentication, and allows users to maintain control over their credentials while providing secure access to your application.
What is PKCE and why is it important for security?
PKCE (Proof Key for Code Exchange) prevents authorization code interception attacks by adding a cryptographic challenge to the OAuth flow. It's especially important for public clients like web applications where the client secret cannot be securely stored.
How do I validate JWT tokens securely on the server side?
Always use the validate() methods provided by Cognito libraries to verify token signatures, expiration dates, and issuer claims. Never decode JWT tokens directly without validation, as this bypasses critical security checks and could allow forged tokens to be accepted.
Ready to Implement Secure Authentication?
AWS Cognito provides a powerful, scalable solution for user authentication that eliminates the complexity of password management while maintaining enterprise-grade security. Start building your secure authentication system today.