What is a free SMS activation verification code?

Obtaining an activation SMS verification code means that users can obtain a one-time verification code by sending SMS when doing some operations that need to verify the mobile phone number, so as to complete the verification and activation operations. Generally speaking, users can get a series of verification codes consisting of numbers or letters by sending the specified short message keywords to the corresponding platform or service provider. The process of obtaining the verification code is usually possible, but the operation is completely controlled by the user.