Authentication Token
A secure string that verifies a user's identity and authorizes access to protected resources.
Definition
An authentication token is a secure credential that proves a user's identity and grants access to protected resources. After successful login, servers issue tokens that clients include with subsequent requests, eliminating the need to send credentials repeatedly.
Common token types include JWTs (JSON Web Tokens) for stateless authentication and session tokens stored server-side. Tokens have expiration times and can be revoked when users log out.
Why It Matters
Tokens are fundamental to secure modern web applications. Understanding token-based authentication helps developers build secure systems and troubleshoot access issues.
For security teams, token management—including secure storage, rotation, and revocation—is critical.
Examples in Practice
A JWT containing user ID and roles, verified by the server using a secret key.
Mobile apps storing refresh tokens securely to maintain login state across sessions.
Single sign-on systems issuing tokens that grant access across multiple related applications.