JSON Web Token (JWT)

JSON Web Token (JWT) is structured by RFC7515: JSON Web Signature or :specs/rfc7516 with certain payload claims. The JWT implementation in Authlib has all built-in algorithms via RFC7518: JSON Web Algorithms, it can also load private/public keys of RFC7517: JSON Web Key:

>>> from authlib.jose import jwt
>>> header = {'alg': 'RS256'}
>>> payload = {'iss': 'Authlib', 'sub': '123', ...}
>>> key = read_file('private.pem')
>>> s = jwt.encode(header, payload, key)
>>> claims = jwt.decode(s, read_file('public.pem'))
>>> print(claims)
{'iss': 'Authlib', 'sub': '123', ...}
>>> print(claims.header)
{'alg': 'RS256', 'typ': 'JWT'}
>>> claims.validate()

The imported jwt is an instance of JWT. It has all supported JWS algorithms, and it can handle JWK automatically. When JWT.encode() a payload, JWT will check payload claims for security, if you really want to expose them, you can always turn it off via check=False.


JWT payload with JWS is not encrypted, it is just signed. Anyone can extract the payload without any private or public keys. Adding sensitive data like passwords, social security numbers in JWT payload is not safe if you are going to send them in a non-secure connection.

You can also use JWT with JWE which is encrypted. But this feature is not mature, documentation is not provided yet.

JWT Payload Claims Validation

JWT.decode() accepts 3 claims-related parameters: claims_cls, claims_option and claims_params. The default claims_cls is JWTClaims. The decode method returns:

>>> JWTClaims(payload, header, options=claims_options, params=claims_params)

Claims validation is actually handled by JWTClaims.validate(), which validates payload claims with claims_option and claims_params. For standard JWTClaims, claims_params value is not used, but it is used in IDToken.

Here is an example of claims_option:

    "iss": {
        "essential": True,
        "values": ["https://example.com", "https://example.org"]
    "sub": {
        "essential": True
        "value": "248289761001"
    "jti": {
        "validate": validate_jti

It is a dict configuration, the option key is the name of a claim.

  • essential: this value is REQUIRED.
  • values: claim value can be any one in the values list.
  • value: claim value MUST be the same value.
  • validate: a function to validate the claim value.