Captcha Purpose : captcha basically use for protect unwanted spam attach and unwanted person hacker, today trend on captcha code mostly use in signup, sign in process,contact us page etc as per user depend reuirement. Note : reCAPTCHA is not working on local or localhost, please run code on live server. What is reCAPTCHA? reCAPTCHA is a free service that protects your website from spam and abuse. reCAPTCHA uses an advanced risk analysis engine and adaptive CAPTCHAs to keep automated software from engaging in abusive activities on your site. It does this while letting your valid users pass through with ease. client side integration link are paste in your page which is show in step 1 in google and paste into header tag your projects, Advantage : 1-main things is reCAPTCHA is prevent spam, 2-robotics attack, 3-essay understand to human, 4-advance sequirites, 5-human effort channeling the time spend solving captcha into digitizing text, 6-captcha can not read by compute...