What is user_activation_key in wordpress

Question

I am new to WordPress and wish to know what is the user_activation_key in the wp_users table? It's like a string of digit with an encrypted code (similar to the password). Why some of the user do not have one.

Answer 1

user_activation_key is one of those keys that WordPress uses for authenticity of a Reset Password request.

So, when you are saying this key is empty for some users, the reason is, those users have never requested for a password reset.

When a password reset is requested a temporary key is generated called check_password_reset_key and sent via email for the reset process.

When the user goes to the generated link, this key is directly compared with user_activation_key. If both keys don't match then it is considered to be an Invalid Request. Otherwise it proceeds and the user will be allowed to enter a new password for his account.

If you want to understand how it works with more details, you can check the wordpress documentation.