Before a form is submitted, validation takes place. This means that required fields must be completed and input values must have a correct format. If something is wrong or missing, an error message will be shown to help the user meet the requirements.

Three types of error messages might appear in your form:

1) An error has occurred: It is necessary to clearly show that an error has occurred when filling out the form. Ideally, this message is shown in red colour;

2) Where the error occurred: It is necessary to highlight the field in which the error occurred;

3) How the error can be fixed: Put information on what needs to be different for the form to be validated correctly.

It’s important to note that the list of errors will be read by screen readers making your website accessible. Once all the checks have passed, the form can be successfully submitted.

When designing forms, we often include both optional and required fields. Typically, we designate a required field by adding an asterisk (*) to it. Although we still find this method applied, it is increasingly being replaced by a different approach that uses words instead of symbols to indicate optional fields. Forms should collect the most important information and have a few optional fields. This will make it easier for people to comprehend the information, without overwhelming them with it.

This method offers a more intuitive approach, particularly for forms that are more extensive and complex.