I agree that most of the authentication belongs on the backend, but there's still the question of how best to handle/recognize authenticated users and authorize

I agree that most of the authentication belongs on the backend, but there's still the question of how best to handle/recognize authenticated users and authorized requests on the frontend. Should I be using JSON web tokens, or cookies? What's the best way to protect routes for users with varying degrees of access? If anything, I'd like to see pros and cons of each strategy, assuming a backend implementation is already in place.