JWT Decoder | Ping Identity Developer Portal (2024)

A JWT (JSON Web Token; pronounced like the word “jot”) is a particular type of token used for sharing claims. Claims are encoded JSON objects that include some information about a subject and are often used in Identity Security applications to transfer information about a user.

For example, after I sign in to a website, information about my account is encoded and passed around to the relevant parties in a JWT. This can enable SSO (Single Sign On); where I needn’t sign in again to another domain owned by the same company, or different companies if trust has been established. Instead, my information can be passed between domains in the JWT, so the second domain knows who I am and that I’ve already been authenticated by a trusted party.

The main benefits of using a JWT are:

Compact representation of information about a subject or user
They can be encrypted or digitally signed so the information can be passed around securely

Components of a JWT

Technically, a JWT is represented as a part of a JWS (JSON Web Signature) object or a JWE (JSON Web Encryption) object. However, the entire string is often referred to as a JWT if the payload is an encoded JWT object.JWTs are always represented using the JWS Compact Serialization or the JWE Compact Serialization.

There are three main parts of a JWS or JWE that include a JWT claim:

Header - the type of encoded object in the payload and any extra encoding
Payload - the JWT claims set
Signature - an encoding of the header and payload

The main parts are encoded then concatenated with a “.” separating them, so that it looks like

{header}.{payload}.{signature}

And this is your JWS or JWE object!

Now, I’ll briefly describe each of these components.

Header

The header includes information about how the JWT claims set, the payload, is encoded. For example, take a look at the following header:

{ “typ”:”JWT”, ”alg”:”HS256”}

This tells us that we have a JWT that is integrity protected with the HMAC SHA-256 algorithm. The payload with a JWE including this header will be of a JWT signed and encrypted with the HMAC SHA-256 algorithm. The type may be left out if the JWSs and JWEs used by the application are JWT types. It’s intended to avoid confusion when different types are being used.

Payload

The payload contains the JWT object itself, and the JWT itself is just a set of claims. For example, take a look at the following payload:

{ “aud”: “https://api.pingone.com”, “iss”: “https://auth.pingone.com/abcdefg12345/as” “exp: “1300819380”}

This payload has an audience (“aud”) of the PingOne for Customers API, an issuer (“iss”) of the PingOne for Customers Authorization Server, and has a set expiration date (“exp”). These are some common claim names, but they will vary depending on the application and service being used.

Signature

The signature is the header and payload (JWT claims set) encoded using the algorithm specified in the header. In our example above it would be the encoded header concatenated with a period and the encoded JWT claims set hashed with the HMAC SHA-256 algorithm.