Umbraco Block Editor Custom View

What is it?

A Block Editor Custom View provides a custom visual representation for blocks in Block List, Block Grid, or Block RTE editors. Instead of the default block rendering, you can create a custom Web Component that displays block content in a specialized way - useful for themed previews, domain-specific visualizations, or enhanced editing experiences.

Documentation

Always fetch the latest docs before implementing:

• Main docs: https://docs.umbraco.com/umbraco-cms/customizing/extending-overview/extension-types/block-custom-view
• Block Editor: https://docs.umbraco.com/umbraco-cms/fundamentals/backoffice/property-editors/built-in-umbraco-property-editors/block-editor
• Foundation: https://docs.umbraco.com/umbraco-cms/customizing/foundation

Related Foundation Skills

• Umbraco Element: For implementing the custom view element
  • Reference skill: umbraco-umbraco-element

Reference Example

The Umbraco source includes a working example:

Location: /Umbraco-CMS/src/Umbraco.Web.UI.Client/examples/block-custom-view/

This example demonstrates a custom block view implementation. Study this for production patterns.

Workflow

1. Fetch docs - Use WebFetch on the URLs above
2. Ask questions - Which block types? Which editors (list, grid, RTE)?
3. Generate files - Create manifest + view element based on latest docs
4. Explain - Show what was created and how to test

Minimal Examples

Manifest (umbraco-package.json)

{
  "name": "My Block Views",
  "extensions": [
    {
      "type": "blockEditorCustomView",
      "alias": "My.BlockView.Hero",
      "name": "Hero Block View",
      "element": "/App_Plugins/MyBlocks/hero-view.js",
      "forContentTypeAlias": "heroBlock",
      "forBlockEditor": "block-list"
    }
  ]
}

Manifest (TypeScript)

import type { ManifestBlockEditorCustomView } from '@umbraco-cms/backoffice/extension-registry';

const manifest: ManifestBlockEditorCustomView = {
  type: 'blockEditorCustomView',
  alias: 'My.BlockView.Hero',
  name: 'Hero Block View',
  element: () => import('./hero-block-view.element.js'),
  forContentTypeAlias: 'heroBlock',
  forBlockEditor: ['block-list', 'block-grid'],
};

export const manifests = [manifest];

Custom View Element (hero-block-view.element.ts)

import { html, css, customElement, property } from '@umbraco-cms/backoffice/external/lit';
import { UmbLitElement } from '@umbraco-cms/backoffice/lit-element';
import type { UmbBlockEditorCustomViewElement, UmbBlockDataType } from '@umbraco-cms/backoffice/block';

@customElement('my-hero-block-view')
export class MyHeroBlockViewElement extends UmbLitElement implements UmbBlockEditorCustomViewElement {
  @property({ attribute: false })
  content?: UmbBlockDataType;

  @property({ attribute: false })
  settings?: UmbBlockDataType;

  render() {
    return html`
      <div class="hero-preview">
        <h2>${this.content?.headline ?? 'No headline'}</h2>
        <p>${this.content?.subheadline ?? ''}</p>
        ${this.content?.backgroundImage
          ? html`<div class="bg-indicator">Has background image</div>`
          : ''}
      </div>
    `;
  }

  static styles = css`
    :host {
      display: block;
    }

    .hero-preview {
      padding: var(--uui-size-space-4);
      background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
      color: white;
      border-radius: var(--uui-border-radius);
      min-height: 100px;
    }

    h2 {
      margin: 0 0 var(--uui-size-space-2);
      font-size: 1.2em;
    }

    p {
      margin: 0;
      opacity: 0.8;
    }

    .bg-indicator {
      margin-top: var(--uui-size-space-2);
      font-size: 0.8em;
      opacity: 0.6;
    }
  `;
}

export default MyHeroBlockViewElement;

declare global {
  interface HTMLElementTagNameMap {
    'my-hero-block-view': MyHeroBlockViewElement;
  }
}

View for Multiple Content Types

const manifest: ManifestBlockEditorCustomView = {
  type: 'blockEditorCustomView',
  alias: 'My.BlockView.Cards',
  name: 'Card Blocks View',
  element: () => import('./card-block-view.element.js'),
  forContentTypeAlias: ['cardBlock', 'featureCard', 'testimonialCard'],
  forBlockEditor: 'block-grid',
};

View for All Blocks in an Editor

// Omit forContentTypeAlias to apply to all blocks
const manifest: ManifestBlockEditorCustomView = {
  type: 'blockEditorCustomView',
  alias: 'My.BlockView.Universal',
  name: 'Universal Block View',
  element: () => import('./universal-view.element.js'),
  forBlockEditor: 'block-list', // Only specify editor type
};

Accessing Settings Data

@customElement('my-styled-block-view')
export class MyStyledBlockViewElement extends UmbLitElement implements UmbBlockEditorCustomViewElement {
  @property({ attribute: false })
  content?: UmbBlockDataType;

  @property({ attribute: false })
  settings?: UmbBlockDataType;

  render() {
    // Settings contain block configuration (colors, layout options, etc.)
    const bgColor = this.settings?.backgroundColor ?? '#ffffff';
    const padding = this.settings?.padding ?? 'medium';

    return html`
      <div style="background-color: ${bgColor}" class="padding-${padding}">
        <h3>${this.content?.title}</h3>
        <div>${this.content?.text}</div>
      </div>
    `;
  }
}

Manifest Properties

Property	Description
forContentTypeAlias	Content type alias(es) this view applies to
forBlockEditor	Editor type(s): block-list, block-grid, block-rte

Element Properties

Property	Type	Description
content	UmbBlockDataType	The block's content data
settings	UmbBlockDataType	The block's settings data

That's it! Always fetch fresh docs, keep examples minimal, generate complete working code.