Security in modern applications is hard to overstate. It's essential to make sure applications have proper measures in place to keep sensitive data out of the wrong hands.
In doing so, two particularly relevant concepts come up, authentication and authorization. They are both referred to in shorthand as "Auth", and often written as AuthN (authentication) and AuthZ (authorization). Because they're used hand in hand when building secure applications, their meanings can get intertwined. This article will help you understand what authentication and authorization are, and how to differentiate between these two important aspects of application security.
Verizon's 2026 Data Breach Investigations Report found credential abuse was the top way attackers got into systems, and OWASP ranks broken access control as the number one risk in web applications. Getting authentication or authorization wrong is how a lot of breaches start.
What is Authentication (AuthN)?
Authentication in computing is defined as the process or action of verifying the identity of a user or process. It's how your application verifies who you say you are. Authentication within the application effectively answers the question "Who are you?".
The goal of authentication is mainly to ensure that only those who have permission can access the application. By verifying the identity of every user, it helps to keep sensitive data safe, block unwanted access, and preserve system security. It's an essential part of the application because in doing so it builds trust between the user and the system.
There are quite a few ways the application can do this:
- We have the classic case of username and password - where the user provides their username and the password which is the key to the user's account. This of course assumes that whoever has the password must be the owner of the account, which in modern security situations is not considered the best approach due to the risk of password leaks, phishing, and other methods bad actors could use to gain identification information.
- Multifactor authentication is another option. To make the system more secure, this technique combines two or more authentication techniques. Usually, it requires utilizing either something you have (like a security token or smartphone), something you know (like a password), or something you are (like a fingerprint or facial recognition). Two-factor authentication (2FA) is the most popular example and it works by sending you a unique code through SMS or an email after you input your username and password. After that, you input this code into the application to have your identification confirmed. That sent code adds an extra layer of security, making it considerably more difficult for unauthorized users to obtain access even if they have access to your device or account. This combination of the account credentials plus an additional factor is what makes it truly "two-factor" authentication.
- Biometric authentication is yet another method of authentication that verifies the user using biometric information. This could be done using the user's bodily characteristics, such as fingerprints, facial IDs, retinal scans, etc., to identify them. Since no two people have the same biometric information, there is very little possibility that an attacker will be able to get around these physical restrictions, making it by far one of the most secure means of verification. This would also mean that the application system must support the hardware that collects the biometric information for verification.
- Single sign-on (SSO) lets a user authenticate once with a central identity provider and then reach every connected application without logging in again. It doesn't change how identity is verified, it changes how often. Behind the scenes the identity provider vouches for the user to each application, which is why SSO usually rides on standards like SAML or OpenID Connect that we cover below.
- Passwordless authentication removes the password entirely and relies on something the user has or is, such as a hardware security key, a passkey stored on the device, or a one-time link sent to a verified email. Passkeys built on the FIDO2 and WebAuthn standards have become common because they resist phishing in a way that shared secrets never could.
These are just a few examples of the various methods used for authentication.
What is Authorization (AuthZ)?
Authorization, on the other hand, is the act of allowing or refusing access to resources within an application. It often takes place following authentication and establishes the resources and permissions that an authenticated user is granted access to. Authorization essentially answers the question, "What are you allowed to do?".
Authorization is essential to make sure users have the right amount of access within the application and it does so by guaranteeing that only those with the required permission have access to specific information. Implementation of authorization contributes to the overall protection of your application from potential security risks.
There are several ways applications can handle authorization, just to name two:
- Role-Based Access Control (RBAC): In this case, users are given permissions according to their positions in an organization. Access rights are tied to specific roles so you could imagine a case where an ordinary user position might only have limited access, whereas an admin might have complete access to all resources. Using this method of authorization makes it so that users only have access to the information necessary for their roles while easing management.
- Attribute-Based Access Control (ABAC): In this method, access is granted according to policies and attributes. User properties (such as department and job title), resource properties, and environmental properties (like access time) can all be considered attributes. ABAC offers you a flexible way to handle authorization Because the decisions made are based on a combination of policies and attributes hence giving you a higher level of control. We compare the two directly in ABAC vs RBAC.
Roles and attributes are the starting point, not the whole story. When access has to depend on the specific resource, the action, and the surrounding context, teams move toward fine-grained authorization, often expressed as policy-based access control. More on that later.
How AuthN and AuthZ Are Carried Around
Once a user is authenticated, the application needs a way to remember it on the next request, and to pass along what that user is allowed to do. This is where tokens come in, and it's a common place where the two concepts get confused.
An ID token is the product of authentication. It says who the user is. It typically carries claims like the user's identifier, name, and email, and it's meant for the application that requested the sign-in.
An access token is the product of authorization. It represents permission to reach a specific resource or API, and it carries what the holder is allowed to do rather than who they are. A service receiving an access token cares about the scope and permissions inside it, not the person's biography.
In practice these are often JSON Web Tokens (JWTs), signed so the receiving service can trust them without a database lookup. The distinction matters because an access token is not proof of identity, and an ID token is not permission to do anything. Treating one as the other is a classic source of security bugs. Sessions play a similar role in traditional web apps, holding a reference to the authenticated user server-side while a cookie carries the session identifier.
The Protocols and Standards Behind AuthN and AuthZ
You rarely build authentication and authorization from raw parts anymore. A handful of open standards do the heavy lifting, and knowing which one handles which job clears up most of the confusion between AuthN and AuthZ.
OAuth 2.0 is an authorization framework. It lets an application get delegated access to a resource on a user's behalf without ever seeing their password. When you let one app "connect" to your account on another, that handoff is usually OAuth. You can read the specification at oauth.net.
OpenID Connect (OIDC) is an authentication layer built on top of OAuth 2.0. OAuth on its own tells you what an app can access, not who the user is, so OIDC adds the identity piece and issues the ID token. The OpenID Foundation maintains it, and it's what most modern "sign in with" flows use.
SAML is an older XML-based standard that handles both authentication and single sign-on, and it's still widespread in enterprise environments where an identity provider federates access across internal applications. The OASIS SAML standard is the reference.
A useful way to hold it in your head is that OAuth 2.0 answers "what can this app do", OpenID Connect answers "who is this user", and SAML has historically done both for enterprise SSO.
There's also a newer effort worth watching. AuthZEN, a standard from the OpenID Foundation, aims to do for authorization what OpenID Connect did for authentication, giving authorization a common interface across apps and services. We wrote about AuthZEN and standards-based authorization if you want the details.
AuthN vs AuthZ: Key Differences and How They Work Together
Verification vs. Permission
As previously stated, authentication and authorization serve distinct functions inside the security system. Authentication is used to confirm the identity of a user or process. Consider it as a way to verify yourself at the door by showing your ID. Authorization, on the other hand, focuses on ensuring that specific users have specific permissions after they enter. Think of it as the key card that allows you access to specific locations or resources depending on your position.
Sequential Process
Authentication always comes before authorization. You could think of it as a 2-step process with authentication always coming first. The system always has to verify who enters it before it can determine what these verified users are permitted to do once they're in.
Integrated Security Approach
They work together quite well despite their differences. You can think of them as two sides of the same coin: authentication ensures that only valid users can access the program, whereas authorization ensures that those users can only access the resources they are authorized to. It's a team effort from both ends that ensures the security of the entire application is not compromised.
Real-World Scenario
Let's take Twitter for example. Before you log into your Twitter account, you have to provide your username and password. That is authentication; you're proving to Twitter you own that account and Twitter makes sure that only you can access it. After logging in, you can send a tweet, change your profile, view, like, and comment on other users' tweets. However, you cannot change or delete other people's accounts or tweets. You have the authority to manage your own content and engage with others, but you cannot control other people's accounts or carry out administrative tasks assigned to Twitter employees. That's authorization in action.
| Aspect | Authentication | Authorization |
|---|---|---|
| Definition | Validates that a user is who they claim to be. It is the first step in accessing a system. | Determines what resources a user can access and what actions they can perform once their identity has been authenticated. |
| Purpose | To verify identity using credentials like passwords, biometrics, or OTPs. | To grant or deny permissions to perform specific actions within a system based on rules or roles. |
| How It Works | Requires users to present evidence of their identity through one or more methods. | Evaluates user permissions based on their authenticated role or attributes within the system. |
| Tools Used | Username/password combinations, biometric scans, one-time PINs, digital certificates. | Access control lists (ACLs), role-based access control (RBAC), attribute-based access control (ABAC), and so on. |
| Standards | OpenID Connect, SAML, FIDO2/WebAuthn. | OAuth 2.0 scopes, AuthZEN, policy engines. |
| Dependency | Independent process usually required at the beginning of a session. | Depends on successful authentication; can't occur unless the user is first authenticated. |
| Outcome | Authentication tokens or sessions that signify the user's identity has been verified. | Access to specific resources like files or databases, and permissions to read, edit, or delete data based on user roles and policies. |
| Security Focus | Focuses on ensuring that users are who they say they are before gaining any access to the system. | Focuses on ensuring that authenticated users are only able to perform actions that they are permitted to, according to security policies. |
Common Mistakes Teams Make With AuthN and AuthZ
A few patterns show up again and again, and most of them come from blurring the line between the two.
The first is assuming authentication is enough. A logged-in user is not the same as an allowed user. Once someone is through the door, authorization still has to decide what they can touch, and skipping that check is exactly how broken access control happens.
The second is scattering authorization logic across the codebase. Permission checks end up hardcoded into controllers, sprinkled through services, and duplicated in every new feature. It works at ten users and breaks at a million, because every rule change now means hunting through code and shipping a deploy.
The third is treating tokens loosely, like trusting an access token as proof of identity, or letting a token carry more scope than the action needs. Least privilege applies to machines and services too, not just people.
The through-line is that authentication is a reasonably solved problem with mature standards, while authorization is where most of the ongoing complexity lives. That's worth keeping in mind when you decide how to build it.
Why Choosing the Right Authorization Solution Matters
Scalability and Flexibility
When it comes to authorization, having a scalable and flexible solution is very important. You want your authorization system to be able to scale as your application grows to accommodate the incoming traffic. A scalable authorization solution can handle an increasing number of users and permissions without compromising performance. Flexibility is equally important because it allows you to easily adjust permissions and roles as your application's requirements change. Both ensure that your system remains efficient no matter how much it grows.
Security Best Practices
Having an effective authorization system is a significant part of maintaining the security of your application. A good authorization setup prevents unauthorized access to sensitive data. By ensuring that only users with the correct permissions can access certain resources, you significantly reduce the risk of security breaches. This not only protects your application but also builds trust with your users.
Outsourcing Complexity
Development teams often have a natural tendency to implement their own in-house authorization solutions, assuming it's an "easy to solve" problem. However, these homegrown solutions typically require significant maintenance and scaling efforts as the application grows in both user base and complexity. Moving authorization out of application code and into a dedicated service, an approach known as externalized authorization, addresses this challenge by shifting the responsibility away from the development team to a finished product that already provides the necessary flexibility and scalability. This approach allows teams to focus on core application features while benefiting from a professionally maintained authorization system.
For guidance on whether to build or buy an authorization solution for your specific use case - feel free to read this blog.
Cerbos Advantages
Cerbos is an authorization management platform built around a few useful ideas. It offers fine-grained control over permissions, so you can create detailed access policies that match the exact needs of your application, gateways, workloads, AI agents, and users. It supports RBAC, ABAC and PBAC - giving you the flexibility to choose the best approach for your situation. Policies live in human-readable YAML, decoupled from your application code, which means product and security teams can change the rules without a release cycle. It integrates with your existing stack and scales as your application grows. There's an open-source version you can integrate for free, available on the Cerbos GitHub repository.
Conclusion
We've covered a lot of ground in this article, diving deep into the world of authentication and authorization. By now, you should have a solid understanding of how these two concepts differ, how they're carried through tokens and standards, and why they're both crucial in keeping your application secure.
To recap, authentication is all about verifying who you are. Authorization is about what you're allowed to do once you're inside. Authentication has largely been solved by mature standards, while authorization is where most teams keep running into new requirements, which is why it pays to get the approach right early.
If you're looking to take your authorization to the next level, it's worth seeing what a dedicated policy engine looks like in practice.
Try Cerbos to see how externalized authorization works without wiring permission logic into your code, or book a call to talk through your setup with the team.
Go deeper:
- Choosing the right authorization deployment (Blog) for a walkthrough of the deployment models
- How to adopt externalized authorization (eBook) for a step-by-step playbook on decoupling authorization from application code
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