Validation Operators

Validations are client-side checks that run after a user submits an answer. They prevent the user from advancing if the answer does not meet the specified criteria.

How Validations Work

The user fills in a question and presses the submit button.
The validations array on that question is evaluated in order.
If any validation fails, its message is displayed as an error (using the screen’s error animation) and the user cannot proceed.
If all validations pass, the rules engine determines the next question.

Validation Structure

Each item in the validations array has this shape:

Field	Type	Required	Description
`op`	string	Yes	The operator to apply (see table below)
`variable`	object	Yes	The value or reference to compare against
`variableEqual`	object	No	A second comparison value (for range checks)
`message`	string	Yes	Error message displayed when validation fails

Variable Object

The variable and variableEqual fields use the same structure as rule variables:

Field	Type	Description
`type`	enum	`static` (fixed value) or `dynamic` (reference another question’s answer)
`value`	any	The comparison value (for `static` type)
`key`	string	Question ID whose answer to use (for `dynamic` type)

Operators

Validation operators match the rule comparison operators but are applied to the current question’s answer rather than determining routing.

Value Comparison

Operator	Description	Example use case
`equals`	Answer must equal the value	“Confirm your email matches”
`notEquals`	Answer must not equal the value	“Cannot use a blacklisted value”
`greaterThan`	Answer must be greater than the value	“Coverage amount must be at least 10,000”
`lessThan`	Answer must be less than the value	“Age must be under 65”
`same`	Loose equality check	Flexible matching
`notSame`	Loose inequality check	Flexible exclusion

Collection Comparison

Operator	Description	Example use case
`isIn`	Answer must be in the provided array	“Must select one of the supported countries”
`isNotIn`	Answer must not be in the provided array	“This country is not supported”
`contains`	Answer must contain the value	“Must include at least one coverage option”
`notContains`	Answer must not contain the value	“Cannot include excluded options”

Existence Check

Operator	Description	Example use case
`isDefined`	Answer must not be null/undefined	“This field is required”
`isNotDefined`	Answer must be null/undefined	Conditional required (used with dynamic variables)

Date Comparison

Operator	Description	Example use case
`dateDiff`	Compare the date answer against a threshold	“Must be at least 18 years old”

The dateDiff validation uses the same structure as rule-date:

{
  "op": "dateDiff",
  "variable": {
    "type": "year",
    "value": 18,
    "dir": "gt",
    "key": "dateOfBirth"
  },
  "message": "You must be at least 18 years old."
}

Country and Address

Operator	Description
`equalsOrContainsCountryCode`	Country code must match
`doesAddressMatch`	Address must match

Examples

Minimum age validation

Ensure the user is at least 18 based on their date of birth:

{
  "op": "dateDiff",
  "variable": {
    "type": "year",
    "value": 18,
    "dir": "gt",
    "key": "dateOfBirth"
  },
  "message": "You must be at least 18 years old to purchase this insurance."
}

Minimum coverage amount

Ensure the entered amount is above a threshold:

{
  "op": "greaterThan",
  "variable": {
    "type": "static",
    "value": 10000
  },
  "message": "The minimum coverage amount is 10,000 EUR."
}

Value must be in allowed list

Ensure the selected country is supported:

{
  "op": "isIn",
  "variable": {
    "type": "static",
    "value": ["DE", "AT", "CH", "FR", "ES"]
  },
  "message": "This product is only available in Germany, Austria, Switzerland, France, and Spain."
}

Cross-question validation (dynamic)

Ensure the end date is after the start date by comparing against another question’s answer:

{
  "op": "greaterThan",
  "variable": {
    "type": "dynamic",
    "key": "travelStartDate"
  },
  "message": "The end date must be after the start date."
}

Required field

Ensure the user has provided an answer:

{
  "op": "isDefined",
  "variable": {
    "type": "static",
    "value": true
  },
  "message": "This field is required."
}

Configuring in Strapi

In the Strapi admin, each question has a validations repeatable component. For each validation entry:

Set the op field to the desired operator.
Configure the variable with either a static value or a dynamic reference to another question.
Write a clear message that tells the user what went wrong and how to fix it.

Validations are evaluated in order. Place the most common failure cases first for the best user experience.