Learn how bearer tokens work in OAuth 2.0 and CIAM. A complete guide for CTOs on bearer token authentication, security risks, and best practices.

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Bearer tokens are possession-based authentication credentials that grant access to anyone holding them, commonly used in OAuth 2.0 workflows. They work through a flow where users authenticate once, receive a short-lived access token (typically 15-30 minutes) and a refresh token for renewal. Key security risks include man-in-the-middle attacks, accidental logging, and XSS vulnerabilities when stored in localStorage. Best practices include aggressive expiration times, refresh token rotation, HTTPS-only transmission, secure storage (HttpOnly cookies or secure enclaves), and proper claims validation. Enterprise implementations often use token exchange patterns to convert SAML assertions into JWT bearer tokens for API compatibility.

Bearer Tokens Explained: Complete Guide to Bearer Token Authentication & Security