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.
 
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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!
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Validate text length

 
Use the min and maximum length validation rules to specify the accept length of text inputs.
 
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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”.
 
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Email validation

 
The “Email input” question type validates email addresses out of the box. Use it to collect emails.
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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.
 
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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.