Form input validation
Collect accurate information from your users by validating form inputs. Define validation rules using logic conditions, regular expressions or out-of-the-box validation rules.
Fillout supports a number of powerful options for validating form questions. Add validation to your forms to ensure you collect accurate information from your users.
Setting a validation rule
Click on the question you would like to add validation for and open the “Validation” section on the right-hand side settings.
Choose a
validation pattern.
Validate with Regular Expressions
Choose the Regex validation pattern to validate a form input with a regular expression. Regular expressions define a rule for the type of input you want to accept.
See here for a list of popular regular expressions. Examples:
Purpose | Regular expression |
Whole numbers | /^\d+$/ |
Alphanumeric without space | /^[a-zA-Z0-9]*$/ |
Alphanumeric with space | /^[a-zA-Z0-9 ]*$/ |
URL | /https?:\/\/(www\.)?[-a-zA-Z0-9@:%.\+~#=]{2,256}\.[a-z]{2,6}\b([-a-zA-Z0-9@:%\+.~#()?&//=]*)/ |
Decimal numbers | /^\d*\.\d+$/ |
Whole and decimal numbers | /^\d*(\.\d+)?$/ |
Copy and paste one of the regular expressions above into the “regex” field. Test your form “preview” mode!
Validate text length
Use the min and maximum length validation rules to specify the accept length of text inputs.
Validate with logic
Choose the Condition validation pattern to validate a form input based on an arbitrary condition.
For example, here we specify that an input must contain either “gmail” or “yahoo”.
Email validation
The “Email input” question type validates email addresses out of the box. Use it to collect emails.
Custom error messages
Provide an
Error message to override the default warning message. For example, here we specified “Your pin must be exactly 6 characters” to be the error message.
Testing validation logic
Go to preview mode and click on the “next” or “submit” button. You’ll see a warning message appear if your inputs don’t match your validation rules.