There actually aren't countless, almost all of them have been broken (many by Google actually), there's just one alternative, hcaptcha, which has been around on

There actually aren't countless, almost all of them have been broken (many by Google actually), there's just one alternative, hcaptcha, which has been around only the past couple years. Back in 2014 when we first added the captcha for too many api requests, there was no other option.