Headless browser detection

There is a headless browser detection test which tests for the following:

• Does the User-Agent contain the string "HeadlessChrome"?
• Is navigator.webdriver set?
• Is window.chrome unset?
• Does the browser skip asking for permissions (like notifications)?
• Are browser plugins unavailable?
• Is navigator.languages unset?

If your browser answers any of these questions with yes, then you fail the test. For more information on the test, check out this post, which is a reply to a post called "Detecting Chrome headless, new techniques".

The author of the latter post also published another test test (code), which claims to be able to detect bots and crawlers. It performs various tests on browser attributes and generates a fingerprint of your browser.

Other "soft" tests done by websites, might include the mouse movement, scrolling behavior, IP address, etc. I doubt you will find many tests regarding these information as this is basically a cat-and-mouse game.