# DocC Support

Marked understands Apple DocC documentation catalogs (`.docc` bundles). When you preview Markdown that lives inside or beside a catalog, Marked can resolve extensionless image references to files in the catalog’s `Resources` folder — including `~dark` and `@2x` variants.

For normal Markdown documents that use paths with file extensions (`images/icon.png`), see Image Variants. That feature works everywhere; DocC resolution is catalog-specific.

Contents

- Enabling DocC resolution
- Extensionless references
- Dark mode and Retina variants
- HTML and Markdown
- File watching
- Related topics

## Enabling DocC resolution

In Marked Settings, Apps pane, enable Resolve DocC image references (on by default).

DocC detection runs when Marked finds a `.docc` catalog ancestor of the open document. No special URL scheme or Xcode integration is required — open the catalog’s Markdown the same way you would any other file.

## Extensionless references

Inside a DocC catalog, authors typically reference images without a path or extension:

    ![Order flow](OrderStateTransitions)

Marked resolves `OrderStateTransitions` to `Resources/OrderStateTransitions.png` (or another supported type) when that file exists in the catalog.

References that already include a path and extension — `images/chart.png` — are left to Image Variants instead and are not rewritten by DocC resolution.

## Dark mode and Retina variants

DocC catalogs often ship multiple files per image:

Role | Example in `Resources/`
--- | ---
Light (1x) | `diagram.png`
Dark (1x) | `diagram~dark.png`
Light (2x) | `diagram@2x.png`
Dark (2x) | `diagram~dark@2x.png`

When more than one variant exists, Marked emits the same responsive `<picture>` markup described in Image Variants. A single-file reference still resolves to a normal `<img>` or `![](Resources/...)` path.

## HTML and Markdown

DocC resolution applies during Marked’s include pass:

- Markdown sources — `![alt](ImageName)` references
- HTML sources — `<img src="ImageName">` without extension

Both are updated before preview rendering.

## File watching

Resolved images under the catalog `Resources` folder are added to Marked’s watch list. Editing a variant file externally updates the preview without a manual refresh.

## Related topics

- Image Variants — `~dark` and `@2x` detection for extension-based paths in any project
- Xcode Playgrounds — preview Swift playground commentary
- Settings: Apps — DocC and image variant preferences

#### Next up: Additional app integrations ▶

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