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.
CarrierWave - Solution for file uploads for Rails, Sinatra and other Ruby web frameworks.
reCAPTCHA - reCAPTCHA is a free security service that protects your websites from spam and abuse.
tus.io - File Uploads
GeeTest CAPTCHA - GeeTest protects your websites, mobile Apps and APIs from bot threats.
Uppy - The next open source file uploader for web browsers