How to detect visitors from Tor?

Question

Nginx

How to most effectively identify visitors using Tor?
I want to selectively display captcha. The application itself is a SPA + separately on the API domain.
Without using Cloudflare.
I guess I should be using something like GeoIP? Determine through nginx? Or another layer? How is this specifically implemented, what services do I have and need?
And on which domain to check - on the one that gives SPA or API? As is usually done in such a bundle ...

Answer 1

Take a list of addresses of output nodes and stuff them, for example, into geo , after which you add a condition. Of course, the relevance of the list will have to be maintained.