When a field is 'required', any unanswered fields will have an orange status button:

In the study forms, the labels of required fields are displayed in bold text. 

The red message ‘This field is required’ is displayed  when a user interacts with the required field but does not provide an answer. 

Only required fields are taken into account when calculating the progress of a participant visits or a survey. 

In Surveys, required fields do not force form completion, therefore users can navigate to the next form page even if they have not completed all required fields - unless stated otherwise in the Survey Package Settings:

Defining a field as required is done in the form editor when creating or editing a field. 

The fields below cannot be set as required:

• Grid fields
• Calculation fields
• Remark
• Summary
• Repeated measure
• Randomization
• Add Report button

It is possible to set the option ‘Required’ for a field to ‘No’ or ‘Yes’  in the ‘Study forms’ editor :