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.
reCAPTCHA - reCAPTCHA is a free security service that protects your websites from spam and abuse.
UniqPin - UniqPin is a free for non-commercial use service which destiny improve ability of interfaces detect...
MTcaptcha - Enterprise Captcha solutions
mosparo - the modern spam protection
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.