hCaptcha - Do you use a captcha to keep out bots? hCaptcha is a drop-in replacement for reCAPTCHA that earns website owners money and helps companies get their data labeled.
Viral Loops - Viral Loops is a viral and referral marketing platform to launch ranking competitions, sweepstakes, pre-launch and referral programs.
MTcaptcha - Enterprise Captcha solutions
Referral Candy - Run a fully automated, customizable and easy to integrate referral program for ecommerce.
GeeTest CAPTCHA - GeeTest protects your websites, mobile Apps and APIs from bot threats.
InviteBox - Acquire new customers with a social referral program. InviteBox is a flexible referral marketing solution that brings you new customers at no cost.