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.
UniqPin - UniqPin is a free for non-commercial use service which destiny improve ability of interfaces detect...
GeeTest CAPTCHA - GeeTest protects your websites, mobile Apps and APIs from bot threats.
visualCaptcha - The best captcha alternative. Accessible, Mobile-friendly, and Retina-ready! Available for Node.js, PHP, Ruby, Meteor, jQuery, Angular, and vanilla JS.
MTcaptcha - Enterprise Captcha solutions
Solve Media - Solve Media's cost per engagement platform offers advertisers branded CAPTCHA and skippable Pre-Roll while providing publishers with enhanced security and a new revenue solution.