RFC 7519 defines a set of optional, standardized claim keys known as Registered Claims to ensure interoperability across applications:

• iss (Issuer): Identifies the principal that issued the JWT.
• sub (Subject): Identifies the principal that is the subject of the JWT (e.g., User ID).
• aud (Audience): Identifies the recipients that the JWT is intended for.
• exp (Expiration Time): Identifies the expiration time on or after which the JWT MUST NOT be accepted.
• nbf (Not Before): Identifies the time before which the JWT MUST NOT be accepted.
• iat (Issued At): Identifies the time at which the JWT was issued.
• jti (JWT ID): Provides a unique identifier for the JWT (used to prevent replay attacks).