Character Set Customization
The Captcha characters can be customized by CharacterSet property. Depending on this value, the Captcha characters are generated. This property accepts string values.
In the ASPX page, include the following Captcha control code-snippet for customized character set.
<ej:Captcha ID="captcha" CharacterSet="qwertyuiop1234" runat="server"></ej:Captcha>
The following screenshot illustrates the Captcha with customized character set.