Validation Rules

Add server-side validation to your form fields. Invalid submissions are rejected with a 400 error and a descriptive message.

Available rules

RuleValueDescription
required—Field must be non-empty
email—Must be a valid email address
minLengthnumberMinimum character length
maxLengthnumberMaximum character length

Configuration

Set validation rules as an array of objects via the dashboard or API. Each rule targets a specific field:

JSON
{
  "validationRules": [
    {
      "field": "name",
      "rule": "required",
      "message": "Please enter your name."
    },
    {
      "field": "email",
      "rule": "required"
    },
    {
      "field": "email",
      "rule": "email",
      "message": "Please enter a valid email address."
    },
    {
      "field": "message",
      "rule": "minLength",
      "value": 10,
      "message": "Message must be at least 10 characters."
    },
    {
      "field": "message",
      "rule": "maxLength",
      "value": 2000
    }
  ]
}

Rule schema

PropertyTypeRequiredDescription
fieldstringYesForm field name to validate
rulestringYesOne of: required, email, minLength, maxLength
valuenumberNoRequired for minLength and maxLength
messagestringNoCustom error message (max 200 chars)
You can add up to 20 validation rules per form. Rules are evaluated in order, and the first failing rule returns its error message.

Error response

When validation fails, AJAX requests receive a JSON error:

JSON
{
  "error": "Please enter your name."
}

Browser submissions see an HTML error page with the message.

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