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Fred supports adding functionality to the Sidebar by adding Sidebar plugins.

Plugins are distributed as MODX Transport Packages, which can be submitted to the MODX Extras repository or uploaded manually from the Installer inside the Manager. You can learn more about how to build Transport Packages in the MODX Documentation, or use a tool like Git Package Management to help create Transport Packages.

Init function

To initialise your plugin start by creating an init function that will be called by Fred. An init function takes three arguments:

  • fred – a reference to the main Fred class
  • SidebarPlugin – the SidebarPlugin class that your plugin has to extend
  • pluginTools – a set of tools you can use in your Plugin to create content and save data. View the source code on Github for a list of available classes, instances and functions which can be used, including:
    • valueParser – parses Template Variables (such as {{theme_dir}}) and replaces them with the correct value based on the given parameters
    • ui – a set of UI elements and inputs to use, including
    • emitter – emits or listen for events
    • Modal – a class to create a modal window
    • fetch – use to make XHR requests
    • fredConfig – an instance of fredConfig
    • utilitySidebar – creates a sidebar, like the one used for Element settings
    • actions - predefined Fred XHR requests
    • Mousetrap - library for keyboard shortcuts

The init function must return a class that extends the SidebarPlugin.


var TestSidebarPluginInit = function(fred, SidebarPlugin, pluginTools) {
    class TestSidebarPlugin extends SidebarPlugin {
        static title = "TestPlugin";
        static icon = "fred--sidebar_more";
        static expandable = true;

        init() {
            this.content = this.render();

        click() {
            return this.content;

        render() {
            const moreList = pluginTools.ui.els.dl();

            const helpLink = pluginTools.ui.els.a(
            helpLink.target = "_blank";


            return moreList;

    return TestSidebarPlugin;

This will create an additional sidebar icon before the More item in the sidebar with the same icon as the More item, three dots.

Icons & Menus

Sidebar icons are dt HTML elements with specific classes. For example, the Settings button from the Sidebar is marked up as follows:

<dt class="fred--sidebar_page_settings" tabindex="0" role="tab">Settings</dt>

The CSS class fred--sidebar_page_settings determines the appearance of the button. To style a new toolbar icon, you need to target the psuedo element ::before in your plugin’s CSS with inline SVG code for a background image:

.fred .fred--sidebar_page_settings:before {
    background: url(data:image/svg+xml, %3Csvg xmlns=http://www.w3.org/2000/svg viewBox=0 0 …35.888-80 80 35.888 80 80 80 80-35.888 80-80z fill=%23fff/%3E%3C/svg%3E)
        center center no-repeat;

Any custom CSS file for your plugin including a custom icon like the above, and other styles needed for the plugin, can be included the same way as the JavaScript file in Register your Plugin step, below.

Fred’s default icons are the SVG versions of Font Awesome 5 icons. You can download the SVG of any icon from its detailed page.

If your plugin needs a menu similar to the Elements or Settings, they are defined inside the dd HTML elements. For example, the Settings menu begins as follows:

    <h3 class="">Settings</h3>
    <form class="fred--page_settings_form">
        <fieldset class="">
            <label class="">Page Title<input class="" type="text"/></label>

The buttons registered to the sidebar are always added before the More button. If there are multiple Sidebar Plugins registered, they will render in the order of the MODX Plugin’s rank in the MODX Manager.

Register your Plugin

When you have the init function returning your plugin's class, you need to register it for Fred by creating a MODX Plugin on the [FredBeforeRender](extras/fred/developer/modx_events) event.

Include the JS file containing the init function using includes and registering the Plugin using beforeRender

To register the toolbar Plugin, you call the registerSidebarPlugin function from Fred with two arguments:

  • name - a unique name for your plugin. Fred cannot register multiple Plugins with the same name.
  • init function - the TestSidebarPluginInit function we created in Init function step, above


$includes = '
    <script type="text/javascript" src="/path/to/plugin/file.js"></script>
    <link rel="stylesheet" href="/path/to/stylsheet/style.css" />

$beforeRender = '
    this.registerSidebarPlugin("TestSidebarPlugin", TestSidebarPluginInit);

$modx->event->_output = [
    'includes' => $includes,
    'beforeRender' => $beforeRender

The Plugin class

The sample Class in the Init function step above can do much more than just show a link to Help page. In fact, much of Fred's functionality is already coded as Plugins. To review the current Sidebar Plugins for a sense of how to create your own, review the source code on Github.

Custom Data

Your Plugin can save and load custom data when the page is saved. Be aware, though, that custom data is only saved when a user saves the entire page.

To save your plugin's data call pluginTools.fredConfig.setPluginsData('Namespace', 'VariableName', 'Data'). This function takes three arguments:

  • namespace - for most cases, use the Plugin's name or something unique to prevent data from being overwritten by another Plugin
  • name - the name of the variable where you want to save the data
  • value - the actual data to store

To load data, call pluginTools.fredConfig.getPluginsData('Namespace', 'VariableName') which takes two arguments:

  • namespace - the same namespace used when calling setPluginsData
  • name - the same name used when calling setPluginsData

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