Learning Redux

Header

The header typically consists of two parts:

• typ: The type of the token (JWT).
• alg: The hashing algorithm used, for example, HMAC SHA256 (HS256) or RSA.

Note that official key names in JWT are only three characters long. This ensures that the token string stays compact.

Each part of the JWT is stored in JSON format and is Base64Url encoded. For example, consider the following header:

{ "alg": "HS256", "typ": "JWT" }

The preceding header becomes this, after encoding:

eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9