What does the verification code refer to?

My verification code is a SMS verification code.

The verification code is a series of randomly generated numbers or symbols that are generated into a picture, which generally prevents batch registration. SMS verification code is an effective verification code system that sends verification codes to mobile phones. Both large websites, especially shopping websites, provide mobile phone SMS verification code functions, which can ensure the security of shopping and verify the correctness of users more accurately and safely. The text message the website sends to your mobile phone contains a string of numbers, which is a verification code. It is usually used to register or bind a mobile phone. Some verification code access providers provide SMS verification code services. Each website sends a request to the access provider's server through the interface. The server sends random numbers or letters to the mobile phone, and the access provider's server performs unified verification of the verification code.

The common verification code is a four-digit, random one-digit string. The most original verification code has almost zero verification effect. CSDN website users use GIF format to log in. Random number pictures are currently commonly used. Verification code, the characters on the picture are quite regular, and the verification effect is relatively good.