jquery-serialize-object is required to add form data to an e

Error message

jquery-serialize-object is required to add form data to an existing data object

What it means

This error is logged by the API module's add.formData() function (api.js:425-450) when settings.serializeForm is true, there is existing data to merge (settings.data is a plain object), and the jquery-serialize-object plugin is not loaded. The module uses $.fn.serializeObject() from that plugin to convert form fields to a JSON object; without it, the module cannot merge form data into the existing settings.data and falls back to replacing it entirely.

Source

Thrown at src/definitions/behaviors/api.js:1134

  // server error
  onError     : function(errorMessage, $module) {},

  // request aborted
  onAbort     : function(errorMessage, $module) {},

  successTest : false,

  // errors
  error : {
    beforeSend        : 'The before send function has aborted the request',
    error             : 'There was an error with your request',
    exitConditions    : 'API Request Aborted. Exit conditions met',
    JSONParse         : 'JSON could not be parsed during error handling',
    legacyParameters  : 'You are using legacy API success callback names',
    method            : 'The method you called is not defined',
    missingAction     : 'API action used but no url was defined',
    missingSerialize  : 'jquery-serialize-object is required to add form data to an existing data object',
    missingURL        : 'No URL specified for api event',
    noReturnedValue   : 'The beforeSend callback must return a settings object, beforeSend ignored.',
    noStorage         : 'Caching responses locally requires session storage',
    parseError        : 'There was an error parsing your request',
    requiredParameter : 'Missing a required URL parameter: ',
    statusMessage     : 'Server gave an error: ',
    timeout           : 'Your request timed out'
  },

  regExp  : {
    required : /\{\$*[A-z0-9]+\}/g,
    optional : /\{\/\$*[A-z0-9]+\}/g,
  },

  className: {
    loading : 'loading',
    error   : 'error'
  },

View on GitHub (pinned to 597843ab84)

Solutions

Include the jquery-serialize-object plugin before Semantic UI's API module: <script src='jquery.serialize-object.js'></script>.
If you do not need to merge form data with existing data, set settings.data to a string or remove it so the form data is used directly (the else branch at api.js:446).
Alternatively, disable settings.serializeForm and serialize form data manually using $(form).serialize().

Example fix

// before
<script src='semantic.min.js'></script>
<script>
$('.form').api({ serializeForm: true, data: { token: 'abc' }, url: '/submit' });
// error: jquery-serialize-object not loaded
</script>

// after
<script src='jquery.js'></script>
<script src='jquery.serialize-object.js'></script>
<script src='semantic.min.js'></script>
<script>
$('.form').api({ serializeForm: true, data: { token: 'abc' }, url: '/submit' });
</script>

Defensive patterns

Strategy: validation

Validate before calling

// Check for the serialize-object plugin before enabling serializeForm
var hasSerializeObject = $.fn.serializeObject !== undefined;
$('.el').api({
  serializeForm: hasSerializeObject,
  url: '/submit'
});
if (!hasSerializeObject) {
  console.warn('jquery-serialize-object not loaded; form serialization disabled.');
}

Type guard

// Type guard: check if jquery-serialize-object is available
function hasSerializeObjectPlugin() {
  return typeof $.fn.serializeObject === 'function';
}

Prevention

Include jquery-serialize-object.js in your build pipeline before Semantic UI.
Add a feature detection check before enabling serializeForm.
Manually serialize form data with $(form).serialize() as an alternative.

When it happens

Trigger: Configuring $('.form').api({ serializeForm: true, data: { extra: 'val' } }) without including the jquery-serialize-object script on the page. The canSerialize variable (api.js:428) checks for $.fn.serializeObject and evaluates to false when the plugin is absent.

Common situations: Forgetting to include jquery-serialize-object.js (a separate dependency from Semantic UI core). CDN or build pipeline dropping the serialize-object plugin. Upgrading Semantic UI and not updating the serialize-object dependency version. The plugin script failing to load due to network issues or incorrect script paths.

Related errors

AI-assisted analysis of Semantic-Org/Semantic-UI@597843ab84 (2026-08-13). Data as JSON: /api/errors/7f2600670ec550c6. Report an issue: GitHub.