What is captcha and when to use it
You may often see the following picture in many websites when you try to post a comment or fill in a contact form.
That is a Captcha.
CAPTCHA stands for Completely Automated Public Turing test to tell Computers and Humans Apart. It is a mechanism to stop automatically posting to a website from a spambot--a computer robot.
If your website is inundated with spam comments or you receive too many spam contact messages that looks like a copy & paste, it is time to implement CAPTCHA. While website owners have total freedom to implement CAPTCHA, here are a few guidelines on when and how to implement a CAPTCHA system. Please notice these are Zoria Media's own guideline. Please consult with your CTO to make your own decision.
Don't implement CAPTCHA unless you have to
CAPTCHA is just one extra thing that visitors to your website need to do and it might annoy some visitors.
Choose the right CAPTCHA system
There are many CAPTCHA systems. The above system is a picture system. You can also use a solver. For example, you can ask what is 2+3. Choose a system that best suit your need. More importantly, choose a system that will not drag down your server performance.
Adjust your challenging level to suit your need
For example, if you choose a solver system, you can challenge what is 7+9 vs what is 732+789. The latter is apparently more difficult than the previous one. Whatever system you are choosing, please choose the best challenging level.
Lastly, always listen to your visitors
If they don't like it, change it.