My logs showed:
416 challenged sessions
99 Turnstile passes
317 no result
So the raw challenge-to-pass rate was 23.8%.
But that should not be read as a 23.8% false-positive rate.
I switched my captcha to Turnstile when installing Bot Guard to have my visitors as little annoyed as possible when running into a captcha. Realistically, with Bot Guard only checking what has passed the other filters before, it improves the existing situation that cannot be further improved by other means. Even if it is not perfect it is better than before. At least that's the way I look at it.Roundtable Research found Cloudflare Turnstile was at the low end of tested bot-detection systems, detecting roughly one third of capable bot sessions. Flipped around, that means a large share of capable bots may still pass.
What would be critical was if normal users became annoyed and went away b/c they would be challenged too frequently or the process of "identifying browser" takes too long or hangs. So this is what the metrics should be about.
If absolutely no one would be filtered out by the captcha it would be of no use at all. If every visitor would pass the browser test it would be of no use. What is critical is the time needed for the browser verification as this is critical (in my eyes more critical than if there is a turnstile captcha) and this should be shown in a potential statistic, preferably with a distribution range between super fast and super slow (in absolute numbers for both, time needed and amount of visitors).
Then the amount and percentage of visitors who got presented with a captcha.
I would (naively) assume, that passing a turnstile captcha should not be a big deal for humans and not really annoying either. On the other hand I did sometimes have the situation myself where I have been locked into a turnstile captcha that kept popping up for no obvious reason. So it not only is not bot-proof but also seems to have it's issues sometimes.
However: Those who would not pass the turnstile captacha are, I'd assume, bots to a very high percentage. If you use a different captcha an unknown amount of regular visitors would probably simply walk away w/o even trying to solve it. So the kind of captcha you use is relevant. Would even be good if one could set it independently from the one used for the registration.





