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Extending With Widgets

The NetlifyCMS exposes an window.CMS global object that you can use to register custom widgets, previews, and editor plugins. The available widget extension methods are:

  • registerWidget: lets you register a custom widget.
  • registerEditorComponent: lets you add a block component to the Markdown editor.

Writing React Components inline

The registerWidget requires you to provide a React component. If you have a build process in place for your project, it is possible to integrate with this build process.

However, although possible, it may be cumbersome or even impractical to add a React build phase. For this reason, NetlifyCMS exposes two constructs globally to allow you to create components inline: ‘createClass’ and ‘h’ (alias for React.createElement).


Register a custom widget.

CMS.registerWidget(name, control, \[preview\])


Param Type Description
name string Widget name, allows this widget to be used via the field widget property in config
control React.Component | string
  • React component that renders the control, receives the following props:
    • value: Current field value
    • onChange: Callback function to update the field value
  • Name of a registered widget whose control should be used (includes built in widgets).
[preview] React.Component, optional Renders the widget preview, receives the following props:
  • value: Current preview value
  • field: Immutable map of current field configuration
  • metadata: Immutable map of any available metadata for the current field
  • getAsset: Function for retrieving an asset url for image/file fields
  • entry: Immutable Map of all entry data
  • fieldsMetaData: Immutable map of metadata from all fields.
  • field: The field type that this widget will be used for.
  • control: A React component that renders the editing interface for this field. Two props will be passed:
    • value: The current value for this field.
    • onChange: Callback function to update the field value.
  • preview (optional): A React component that renders the preview of how the content will look. A value prop will be passed to this component.


<script src="https://unpkg.com/netlify-cms@^0.7.0/dist/cms.js"></script>
var CategoriesControl = createClass({
  handleChange: function(e) {
    this.props.onChange(e.target.value.split(',').map((e) => e.trim()));

  render: function() {
    var value = this.props.value;
    return h('input', { type: 'text', value: value ? value.join(', ') : '', onChange: this.handleChange });

var CategoriesPreview = createClass({
  render: function() {
    return h('ul', {},
      this.props.value.map(function(val, index) {
        return h('li', {key: index}, val);

CMS.registerWidget('categories', CategoriesControl, CategoriesPreview);


Register a block level component for the Markdown editor:



  • definition: The component definition; must specify: id, label, fields, patterns, fromBlock, toBlock, toPreview


<script src="https://unpkg.com/netlify-cms@^0.7.0/dist/cms.js"></script>
  // Internal id of the component
  id: "youtube",
  // Visible label
  label: "Youtube",
  // Fields the user need to fill out when adding an instance of the component
  fields: [{name: 'id', label: 'Youtube Video ID', widget: 'string'}],
  // Pattern to identify a block as being an instance of this component
  pattern: /youtube (\S+)\s/,
  // Function to extract data elements from the regexp match
  fromBlock: function(match) {
    return {
      id: match[1]
  // Function to create a text block from an instance of this component
  toBlock: function(obj) {
    return 'youtube ' + obj.id;
  // Preview output for this component. Can either be a string or a React component
  // (component gives better render performance)
  toPreview: function(obj) {
    return (
      '<img src="http://img.youtube.com/vi/' + obj.id + '/maxresdefault.jpg" alt="Youtube Video"/>'