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Authentication checks whether an identity claim is valid; authorization decides what that verified subject may access or do. A successful sign-in therefore does not automatically grant access to every page or action.
What authentication and authorization mean
Authentication: verifying an identity claim
NIST defines authentication as “verifying the identity of a user, process, or device,” often as a prerequisite to allowing access to information-system resources. In plain terms, the system checks whether the account or device making a request is who or what it claims to be. The NIST CSRC Glossary definition of authentication describes that role.
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Authorization: deciding what access is allowed
Authorization concerns privileges and access decisions. NIST describes it as the decision to permit or deny a subject access to system objects, such as networks, data, applications, or services. A system may also assign or enforce particular privileges. See the NIST CSRC Glossary definition of authorization and NIST’s Guide to Attribute Based Access Control (ABAC) Definition and Considerations.
How the decisions differ
| Comparison | Authentication | Authorization |
|---|---|---|
| Question | Who or what is making this request? | What may this subject access or do? |
| What it evaluates | An identity claim and evidence used to verify it, such as an authenticator | Applicable privileges or policy, and potentially details of the request |
| Typical result | Confidence that the claim is valid, or failure to verify it | A decision to permit or deny access, possibly with specified privileges |
| Illustrative failure | Credentials do not verify the claimed account | The signed-in account lacks the required role or grant |
NIST SP 800-162 states directly: “Authentication is not the same as access control or authorization.” The distinction matters because verifying an identity does not, by itself, determine that identity’s access rights.
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Why being logged in may not let you access a page
Consider a workplace app. A person signs in with credentials, and the app verifies the account. That is authentication. The person then requests a payroll record or attempts to administer a team. The app must separately determine whether the account has permission for that particular resource or action. An authenticated employee might be allowed to view ordinary work information but not payroll records or administrative controls.
This is an illustration of the distinction, not a claim about how any specific product implements its checks. A denial after sign-in can mean that authentication succeeded while authorization did not permit the requested action.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Where identification fits
Identification is a third, related concept: it is the claim about which identity is making the request. Authentication establishes confidence in that claim; authorization determines and enforces what the resulting subject may access. NIST IR 8014 discusses identification, authentication, and authorization as parts of identity management; they are connected, but they are not interchangeable.
- Identify: a request names or otherwise claims an account, user, process, or device.
- Authenticate: the system verifies the claim to an appropriate level of confidence.
- Authorize: the system evaluates whether the subject may perform the requested action on the requested resource.
This sequence is a teaching model, not a universal architectural rule. Systems can distribute or combine these functions, and the order can vary. The important distinction is between verifying a subject and making an access decision.
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How to use the distinction when troubleshooting
- If sign-in fails, check the identity claim and the authentication method or credentials.
- If sign-in succeeds but a particular page or action is denied, check whether the account has the required permission, role, or policy approval for that resource and action.
- If the access decision seems wrong, confirm that the request is being made with the intended account and that the relevant access rules or grants cover the requested operation.
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