# Loader

Controls every busy indicator the SDK shows: the veil while a tool prepares its UI (for example Manage Pages preparing the page tiles of a large document), and the full-screen document loader when you pass the same object to [`PDFViewer.showLoadingIndicator(container, { loader })`](https://kernstra.com/docs/web-sdk/api/pdfviewer/showloadingindicator) — it runs before the viewer exists, so it cannot read the viewer's config.

- Interface: `LoaderConfig`
- Config path: `config.loader`

## Example

```ts
const viewer = new PDFViewer(container, doc, {
  loader: { html: '<img src="/acme-logo.svg" width="72" alt="Loading" />' },
});
```

## Options (2)

### `html`

- Type: `string`
- Default: `SDK spinner; '' an empty block`
- Page: https://kernstra.com/docs/web-sdk/config/loader/html

Custom loader markup (a branded logo), put into the page as HTML: your own markup only, never a user's. It is injected verbatim (it is your own trusted configuration), so a branded loader is one line.

### `text`

- Type: `string`
- Default: `the viewer.loading string`
- Page: https://kernstra.com/docs/web-sdk/config/loader/text

Label under the default spinner; ignored when `html` is set. `text` labels the document loader only; the busy veil shows no text. A `text` left out shows the default label; `text: ''` shows none.

## Notes

Busy indicators are armed with a 150ms delay for regular tool activation, so fast operations never flash a loader; known-slow operations (Manage Pages on big documents) show it immediately.

The static document loader takes the same object: `PDFViewer.showLoadingIndicator(container, { loader })`. Pass your `locale` beside it — `PDFViewer.showLoadingIndicator(container, { loader, locale })` — so the default label is in your users' language (see [Locale](https://kernstra.com/docs/web-sdk/config/locale)).


Web page: https://kernstra.com/docs/web-sdk/config/loader