OAuth 2.0 is an authorization framework for delegated access; it defines flows and token usage, not a token format. JWT is a token format that can carry signed claims. A JWT must be validated for signature, issuer, audience, expiry, and relevant claims. Opaque tokens can instead be checked through introspection or a server-side store. Choose based on revocation needs, trust boundaries, token size, and operational complexity; never treat decoding as validation.