I just did research few days back, and there are none that aren't passable with some OCR/tensorflow tech. Anything simple and the question is why do you need it

I just did research few days back, and there are none that aren't passable with some OCR/tensorflow tech. Anything simple and the question is why do you need it ? Anything hard enough for bots not to beat it will also fail many humans. Add rate limiter instead and put CF infront or something similar. Way better experience then any captcha. In case you still want it here is solid one: https://github.com/dchest/captcha https://github.com/dchest/captcha