It's jsonld, using w3c verifiable credentials. (https://www.w3.org/TR/vc-data-model/ https://www.w3.org/TR/vc-data-model/). Using the context (https://www.w3.or

It's jsonld, using w3c verifiable credentials. (https://www.w3.org/TR/vc-data-model/ https://www.w3.org/TR/vc-data-model/). Using the context (https://www.w3.org/2018/credentials/v1 https://www.w3.org/2018/credentials/v1) you can look up information about the properties and types, in principle. (It also also includes a link to a json schema)