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Authentication verifies who or what is requesting access; authorization determines whether that subject may access a particular resource or perform an action. You can sign in successfully and still be denied permission to open a file or use a feature.
What authentication and authorization mean
Authentication: verifying identity
Authentication checks the identity claimed by a user, process, or device. In plain language, it answers, “Who are you?” A system uses evidence from an authenticator to establish confidence in that identity. NIST describes authentication as verifying the identity of a user, process, or device, often as a prerequisite to access (NIST glossary: authentication).
Common examples of authentication evidence include something a person knows, such as a password or PIN; something they possess, such as a cryptographic device or token; or something they are, such as a biometric. These examples help establish identity; they do not define the account’s permissions (NIST glossary: authenticator).
Authorization: deciding what is permitted
Authorization evaluates privileges or makes a decision about whether a subject may access an object or carry out an action. In plain language, it answers, “What are you allowed to access or do?” A policy or permission set can allow or deny a request. NIST describes authorization in terms of privileges granted to a user, program, or process, and as the decision to permit or deny a subject access to system objects (NIST glossary: authorization).
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Authentication vs. authorization at a glance
| Aspect | Authentication | Authorization |
|---|---|---|
| Purpose | Establishes confidence in a claimed identity. | Determines privileges or whether a request is allowed. |
| Question | Who or what is making the request? | May this subject access this resource or perform this action? |
| Typical inputs | Evidence from an authenticator, such as a password, token, or biometric. | The subject, requested resource or action, and applicable permissions or policy. |
| Common place in a request flow | Often occurs before an access decision. | Evaluates the requested access; the exact flow depends on the system’s architecture. |
| Possible result | The claimed identity is verified to the system’s required level, or verification fails. | The requested access or action is permitted or denied. |
Can you be authenticated but not authorized?
Yes. For example, signing in to a company account can authenticate an employee, while a later request to view payroll records is denied because that employee does not have permission to see them. The login establishes identity; it does not automatically grant access to every company resource.
Authentication and authorization are connected in many sign-in-and-access experiences, but they remain separate checks. NIST’s guide to attribute-based access control states that “Authentication is not the same as access control or authorization” (NIST SP 800-162).
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How to tell which check is failing
- Authentication problem: The system cannot verify the claimed identity—for example, the credentials or required verification evidence are not accepted.
- Authorization problem: The system recognizes the account, but the requested resource or action is outside its permissions.
This distinction is useful when diagnosing access trouble: a successful sign-in does not prove that an account has permission to do everything the application offers. Systems differ in how they implement the request flow and evaluate policy, so the concepts do not imply one universal sequence or authorization engine.
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