You can validate the following open-ended question types to require that people enter their answer in a specific format:
It's not possible to add answer validation to a Comment Box question type.
Answer validation is triggered when a survey taker clicks the Next or Done button at the bottom of the survey.
To validate a textbox question:
You can quickly validate the Multiple Textboxes question type to allow only numerical data (positive whole numbers), and to reveal the option to require a fixed sum.
To only allow numerical data for a Multiple Textboxes question:
To validate a Date/Time question to only collect dates in a specific format:
If people enter the wrong date format, they’ll see a message letting them know how to fix their answer. It’s not possible to customize this message.
If you add an "Other" textbox to a close-ended Multiple Choice, Dropdown, or Matrix question, you can validate that field to require respondents to enter their answer in a specific format. Learn more: Validating "Other" Textboxes