Depends on the implementation, with Stripe you can embed their widgets directly on your website to save some development time, but you can also implement in the

Depends on the implementation, with Stripe you can embed their widgets directly on your website to save some development time, but you can also implement in the backend. Even though you would implement it in the backend, there is usually some details leaking (on purpose obviously) to the frontend, like identifiers (Stripes IDs are usually pretty easy to spot) or even the structure of the data can tell you which provider.