Server-Side Field Validation Rules

formcarry provides server-side field validations so you can enforce data quality rules without writing any backend code. Rules are configured per field in your form’s Settings, and formcarry evaluates every incoming submission against them automatically. When a submission fails validation, formcarry returns an HTTP 422 response with a structured error object that tells you exactly which fields failed and why.

Available Validators

Validator	Description
`Required`	Field cannot be empty
`Number`	Field must be a number
`Email`	Field must be a valid email address
`Url`	Field must be a valid URL
`Contains`	Field must contain the specified value
`NotContains`	Field must not contain the specified value

Validation Error Response

When one or more validation rules fail, formcarry responds with HTTP 422 and a JSON body:

{
  "code": 422,
  "status": "error",
  "title": "Validation Failed",
  "message": "The email must be a valid email address. (+1 more errors)",
  "errors": {
    "email": {
      "message": "The email must be a valid email address.",
      "rule": "email"
    },
    "name": {
      "message": "The name field is mandatory.",
      "rule": "required"
    }
  }
}

The errors object is keyed by field name, making it straightforward to map each error back to the corresponding input in your form.

Displaying Errors in Your Form

You can use the form-error CSS class (or any class of your choosing) to visually highlight inputs that failed validation. The following examples show how to parse the errors object and apply the class to the matching form elements.

document.querySelector('.ajaxForm').addEventListener('submit', function (e) {
  e.preventDefault();

  fetch('https://formcarry.com/s/yourFormId', {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
      'Accept': 'application/json',
    },
    body: JSON.stringify({ email: 'wrongEmail', name: '' }),
  })
    .then((response) => response.json())
    .then((response) => {
      if (response.code === 422) {
        var errors = response.errors;
        for (var key in errors) {
          if (errors.hasOwnProperty(key)) {
            var formElement = document.querySelector('[name="' + key + '"]');
            if (formElement) {
              formElement.classList.add('form-error');
            }
          }
        }
        alert('An error occurred: ' + response.message);
      } else {
        alert('We received your submission, thank you!');
      }
    })
    .catch((error) => console.log(error));
});

$(function () {
  $('.ajaxForm').submit(function (e) {
    e.preventDefault();
    var href = $(this).attr('action');

    $.ajax({
      type: 'POST',
      dataType: 'json',
      url: href,
      data: $(this).serialize(),
      success: function (response) {
        if (response.code === 422) {
          $.each(response.errors, function (key) {
            $('[name="' + key + '"]').addClass('form-error');
          });
          alert('An error occurred: ' + response.message);
        } else {
          alert('We received your submission, thank you!');
        }
      },
    });
  });
});

Styling Error Inputs

Add a CSS rule for .form-error to give users a clear visual signal that a field needs attention:

.form-error {
  border: 2px solid red;
  background-color: #ffe6e6;
}

This adds a red border and a light red background to any input that failed validation. Adjust the colors and properties to match your site’s design.

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Server-Side Field Validation Rules

Available Validators

Validation Error Response

Displaying Errors in Your Form

Styling Error Inputs

​Available Validators

​Validation Error Response

​Displaying Errors in Your Form

​Styling Error Inputs

Available Validators

Validation Error Response

Displaying Errors in Your Form

Styling Error Inputs