By default, a UUID is issued as an id_token in WSO2 Identity Server, which is of the first type above. But, it also can be configured to issue a self-contained id_token (JWT), which is of the second type above.

- Open the `<IS_HOME>/repository/conf/identity/identity.xml` file and uncomment the following entry under `<OAuth>` element.

```
<IdentityOAuthTokenGenerator>org.wso2.carbon.identity.oauth2.token.JWTTokenIssuer</IdentityOAuthTokenGenerator>
```