What is authentication?
Authentication is the process of verifying the identity of a user or system. It's about confirming: “Who are you?”
Common authentication methods include:
- Username and password
- OAuth providers (Google, GitHub, etc.)
- Biometric verification
- Two-factor authentication (2FA)
When a user successfully authenticates, they are typically issued a token or session that proves their identity to the system.
What is authorization?
Authorization is the process of determining what resources or actions an authenticated user is allowed to access. It answers the question: “What can you do?”
Examples:
- Can this user access the admin dashboard?
- Is this user allowed to edit or delete a post?
- Does this user have access to premium features?
Authorization usually happens after authentication and depends on roles, permissions, or ownership of resources.
Key differences
| Feature | Authentication | Authorization |
| Purpose | Verifies identity | Grants access rights |
| Question answered | Who are you? | What can you do? |
| Performed first? | ✅ Yes | ❌ No (comes after authentication) |
| Data involved | Credentials (e.g., username, password) | Permissions, roles, resource ownership |
| Example | Logging in with email/password | Accessing admin-only routes |
Common technologies used
Authentication:
- JWT (JSON Web Tokens)
- Passport.js
- Firebase Auth
- OAuth 2.0 / OpenID Connect
Authorization:
- Role-based access control (RBAC)
- Access control lists (ACL)
- Attribute-based access control (ABAC)
Real-world example
Imagine a blogging platform:
- Authentication:
The user logs in with email and password — they are now identified.
- Authorization:
Once logged in:
- A regular user can read and comment on posts.
- An author can write and edit their own posts.
- An admin can delete any post or ban users.
Best practices
- Keep authentication and authorization logic separate
- Never expose protected resources without proper authorization checks
- Use HTTPS to protect authentication credentials
- Always validate and verify JWTs or session tokens
- Implement role-based checks server-side, even if also present on the client
Conclusion
Authentication and authorization are often confused but serve distinct purposes. Authentication confirms identity, while authorization defines what that identity is allowed to do. Both are essential to building secure, trustworthy web applications.