Agent skill
umbraco-file-upload-preview
Implement file upload preview components in Umbraco backoffice using official docs
Install this agent skill to your Project
npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/data/umbraco-file-upload-preview
SKILL.md
Umbraco File Upload Preview
What is it?
File Upload Previews are custom web components that render previews for specific file types during upload in Umbraco. They allow you to create visual representations for files based on their MIME types, such as displaying thumbnails for images, waveforms for audio, or custom icons for specific file formats.
Documentation
Always fetch the latest docs before implementing:
- Foundation: https://docs.umbraco.com/umbraco-cms/customizing/foundation
- Extension Registry: https://docs.umbraco.com/umbraco-cms/customizing/extending-overview/extension-registry
- Umbraco Element: https://docs.umbraco.com/umbraco-cms/customizing/foundation/umbraco-element
Related Foundation Skills
- Umbraco Element: Base class for creating UI components
- Reference skill:
umbraco-umbraco-element
- Reference skill:
Workflow
- Fetch docs - Use WebFetch on the URLs above
- Ask questions - What MIME types? What preview display?
- Generate files - Create manifest + element based on latest docs
- Explain - Show what was created and how to test
Minimal Examples
Manifest (manifests.ts)
export const manifests: Array<UmbExtensionManifest> = [
{
type: 'fileUploadPreview',
alias: 'My.FileUploadPreview.Custom',
name: 'Custom File Upload Preview',
weight: 100,
element: () => import('./my-file-preview.element.js'),
forMimeTypes: ['application/pdf', 'application/x-pdf'],
},
];
Element Implementation (my-file-preview.element.ts)
import { html, customElement, property, state } from '@umbraco-cms/backoffice/external/lit';
import { UmbLitElement } from '@umbraco-cms/backoffice/lit-element';
import type { UmbFileUploadPreviewElement } from '@umbraco-cms/backoffice/media';
@customElement('my-file-preview')
export class MyFilePreviewElement extends UmbLitElement implements UmbFileUploadPreviewElement {
@property({ type: Object })
file?: File;
@state()
private _previewUrl?: string;
override updated(changedProperties: Map<string, unknown>) {
if (changedProperties.has('file') && this.file) {
this._previewUrl = URL.createObjectURL(this.file);
}
}
override disconnectedCallback() {
super.disconnectedCallback();
if (this._previewUrl) {
URL.revokeObjectURL(this._previewUrl);
}
}
override render() {
if (!this.file) return html``;
return html`
<div class="preview-container">
<uui-icon name="icon-document"></uui-icon>
<span>${this.file.name}</span>
</div>
`;
}
}
export default MyFilePreviewElement;
Interface Reference
interface ManifestFileUploadPreview extends ManifestElement<UmbFileUploadPreviewElement> {
type: 'fileUploadPreview';
forMimeTypes: string | Array<string>; // e.g., 'image/*', ['image/png', 'image/jpeg']
}
interface UmbFileUploadPreviewElement {
file?: File;
}
Common MIME Type Patterns
image/*- All image typesvideo/*- All video typesaudio/*- All audio typesapplication/pdf- PDF files*/*- Fallback for all types (use with lower weight)
That's it! Always fetch fresh docs, keep examples minimal, generate complete working code.
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