How to write the format of verification code

1, four-digit, random one-digit string, the most original verification code, the verification effect is almost zero. 2.CSDN website users log in in GIF format, which is a commonly used random digital picture verification code.

2, Chinese characters, QQ website registration at present the latest verification code, are Chinese characters, randomly generated.

3.QQ website users log in in PNG format, and the pictures use random numbers and random capitalized English letters. The whole composition is a bit grandiose, and every character will change his position every time he refreshes! Sometimes the pictures are unrecognizable to the human eye.

4. The hotmail application of 4.MS is BMP format, with random number+random capitalized English letters+random interference pixels+random position.

5, Korean or Japanese, now you have to type Korean to register MS on HF.

6. Google registered Gmail in JPG format, with random English letters+random color+random location+random length.

7. Other major forums are in XBM format, and the content is optional.