WHMCS supports various field types for custom fields. Each field type serves a different purpose and is suited for collecting different kinds of information. Here are the field types available in WHMCS:

1. Text Box:

   • A single-line text input field where users can enter short text or numbers.

2. Multiline Text Box:

   • A larger text input field that allows users to enter multiple lines of text.

3. Checkbox:

   • A field with a checkbox that users can select or deselect.

4. Radio Buttons:

   • A set of options where users can select only one option from the available choices.

5. Dropdown Menu:

   • A menu with a list of options where users can select one option from the list.

6. Date Picker:

   • A field with a calendar widget that allows users to select a date.

7. Password:

   • A field for entering passwords, with the text masked for security.

8. File Upload:

   • Allows users to upload files (e.g., documents, images) through a browse button.

9. Link:

   • A field for entering a URL or a link.

10. Email:

    • Validates that the input conforms to the structure of an email address.

11. Country:

    • A drop down menu with a list of countries.

12. Language:

    • A drop down menu with a list of languages.

13. Custom:

    • Allows you to create a custom field that can be dynamically filled using a hook or API call.

These field types provide flexibility in collecting various types of information from clients, whether it's basic contact details, preferences, or specific requirements. When creating custom fields, it's important to choose the appropriate field type based on the information you want to collect.