octobercms/october · error · Error

The browser does not support the FormData interface.

Error message

The browser does not support the FormData interface.

What it means

Thrown by the Options constructor in October CMS's AJAX framework when typeof FormData === 'undefined'. The AJAX layer builds POST bodies with the FormData interface, so a JS environment without it (IE9 and older, some embedded WebViews, or server-side/SSR execution of the bundle) cannot issue requests and the constructor fails fast.

Source

Thrown at modules/system/assets/js/framework.js:330

      const op = this.getOps("redirect")[0];
      return op?.url || this.redirect || null;
    }
    getReload() {
      return this.getOps("reload")[0] || null;
    }
  };

  // ../../vendor/larajax/larajax/resources/src/request/options.js
  var Options = class {
    constructor(handler, options) {
      if (!handler) {
        throw new Error("The request handler name is not specified.");
      }
      if (!handler.match(/^(?:\w+\:{2})?on*/)) {
        throw new Error('Invalid handler name. The correct handler name format is: "onEvent".');
      }
      if (typeof FormData === "undefined") {
        throw new Error("The browser does not support the FormData interface.");
      }
      this.options = options;
      this.handler = handler;
    }
    static fetch(handler, options) {
      return new this(handler, options).getRequestOptions();
    }
    // Public
    getRequestOptions() {
      return {
        method: "POST",
        url: this.options.url ? this.options.url : window.location.href,
        headers: this.buildHeaders()
      };
    }
    // Private
    buildHeaders() {
      const { handler, options } = this;

View on GitHub (pinned to b608633a7e)

Solutions

1. Guard the call: if (typeof FormData === 'undefined') return; before invoking oc.request()/oc.ajax()
2. Polyfill FormData in the offending environment (formdata-polyfill, whatwg-fetch era polyfills)
3. In SSR/Node tests, stub global FormData or skip framework.js execution on the server
4. For legacy browsers, serve a legacy build/polyfill bundle conditionally

Example fix

// before
import '~/modules/system/assets/js/framework-bundle.js'; // SSR: throws on request

// after
if (typeof FormData !== 'undefined') {
  oc.request(el, 'onSave');
}

if (typeof FormData === 'undefined') {
  console.warn('This browser/runtime lacks FormData - AJAX requests disabled');
} else {
  oc.request(el, 'onSave');
}

const supportsFormData = () => typeof FormData !== 'undefined';

try { oc.request(el, 'onSave'); } catch (e) { if (/does not support the FormData/.test(e.message)) { /* polyfill or degrade gracefully */ } else throw e; }

When it happens

Trigger: Loading framework.js in Node/headless SSR and calling oc.request(); running the site in a legacy browser (IE9 and earlier); a stripped-down embedded WebView lacking the FormData API; test environments (jsdom beforeFormData was polyfilled).

Common situations: Server-side rendering accidentally executing the AJAX bundle; supporting legacy kiosk/intranet browsers; unit tests in Node that import the bundle without a DOM polyfill; rare mobile WebViews from the pre-2013 era.

Related errors

• The titleProperty property should be specified in the object
• The itemProperties property should be specified in the objec
• Object list key property ${this.propertyDefinition.keyProper
• Object list value should be an object. Property: ${this.prop
• Values not found for the selected row.

AI-assisted analysis of octobercms/october@b608633a7e (2026-08-21). Data as JSON: /api/errors/c2f48fc9d7eab638. Report an issue: GitHub.