Configure Form Validation Messages

Overview

Validation is configured per field in the Form Designer. Each field has a Validation tab where you can set a custom error message, add one or more validator rules, and define a maximum input length.

Validators check what the user has entered and block the form from progressing if the value doesn't match. If the field is left blank or fails a validation rule, the error message you've set is shown to the user.

‍

Open the Validation tab

Open the form template, go to the Template tab, and select Form Designer.
Click Edit on the question you want to configure.
Click the Validation tab.

‍

Required error text

This is the message shown to a user when they try to proceed without filling in a field that's marked as mandatory. By default, fields show a generic platform message — entering your own text here lets you write something more specific and on-brand.

Keep required error messages direct and action-oriented. "Please enter your email address" is clearer than "This field is required."

‍

Validators

Validators check the format or content of a user's input against a rule you define. A field can have more than one validator. To add one, click + Add a new item and select the validator type from the dropdown.

Validator	What it checks
e-mail	Checks that the value is a correctly formatted email address (e.g. `name@domain.com`). Use this on any email input field.
numeric	Checks that the value contains only numbers. Useful for fields like account numbers, phone numbers, or postcode fields where letters should be rejected.
text	Validates against a minimum and/or maximum character count. Use this when you need to enforce a specific length range — for example, a reference number that must be exactly 8 characters.
regex	Validates the input against a regular expression pattern you define. The most flexible option — use it for custom formats like phone numbers, postcodes, date formats, or any pattern not covered by the other validators.
expression	Validates using a custom logic expression that can reference other fields in the form. Use this for cross-field validation — for example, checking that a confirmation email field matches the email field above it.

‍

Each validator type has its own configuration options — such as the regex pattern, the expression to evaluate, or the min/max character counts for the text validator. These appear beneath the validator type once you've added it.

You can also set a custom error message per validator so users see a specific, helpful message when that rule fails — for example, "Please enter a valid email address" for the e-mail validator rather than a generic error.

‍

Maximum length

Sets an upper limit on the number of characters a user can enter in the field. The default value is -1, which means no limit is applied. Set a specific number to cap the input length — useful for fields like reference numbers, postcodes, or any field where an overly long entry would indicate a mistake.

‍

Save your changes

Click Apply to preview the settings without closing the editor, or OK to confirm and close.
Click Save in the Form Designer once all fields are configured.
Use Test Form to submit test values and confirm each validator fires and displays the correct error message.

‍Making a field mandatory: The Validation tab controls error messages and validator rules, but the mandatory/optional status of a field is set in the General tab. Tick Required there first, then come back to Validation to customise the error message that appears when the field is left blank.

‍

Well-written validation messages are one of the easiest ways to reduce form abandonment — clear, specific guidance helps users correct mistakes quickly rather than guessing what went wrong.

‍