how to detect selenium/webdriver browsing on my site

Does anyone know how to detect selenium/webdriver browsing on my site?

I don't want to block them, just detect them.

I saw this question: Can a website detect when you are using selenium with chromedriver?

But trying all of these on latest version didn't seem to work.

Any body knows anything else?

P.S. please don't leave answers/comments of "dont block"/"you are looking in the wrong place" - I am fully aware of what I'm asking and what will be the business logic to use it.

-- EDIT --

Things I have tested from the link above:

  1. detecting cdc_asdjflasutopfhvcZLmcfl_ key on elements, mostly on window and document but some other elements we have across the entire site.

  2. Searching for window.navigator.webdriver always returns undefined instead of true (tested on both chrome and firefox although only firefox said to support it)

  3. tested the script from this answer:

All tests were done using latest selenium, browsers (firefox and chrome), and latest webdriver plugins. for now only on windows, but will probably test ubuntu as well.