I misunderstood your question. The library I posted only works for JWT which you are moving away from.
Verify uses the secret_key_base configured in your Endpoint which you should not expose to your front-end (this would compromise your app’s security). It’s easier to make a new endpoint, send the token to the endpoint and validate server-side and return the decoded values.
According to this thread: How is Phoenix.Token different from JWT?
Phoenix.Token is base64 encoded erlang terms. You could try and decode using a base64 decoder and see what the result is: https://www.base64decode.org/ but even then you will have to parse the Erlang terms into JSON.
