# Slide options

## Front matter

| Key           | Example                                | Effect                                                   |
| ------------- | -------------------------------------- | -------------------------------------------------------- |
| `title`       | `Lorem ipsum`                          | deck title (footer `{title}`, browser tab, galleries)    |
| `author`      | `Dolor Sit`                            | footer `{author}`                                        |
| `description` | `"…"`                                  | galleries and HTML description                           |
| `aspectRatio` | `16:9`, `4:3`                          | design size 1280×720 or 1024×768                         |
| `theme`       | `light`, `dark`, `system` or an object | default mode or theme overrides                          |
| `lang`        | `en`, `fr`                             | interface language (controls, presenter console, remote) |
| `footer`      | `false` or an object                   | disables or overrides the footer                         |
| `rules`       | object                                 | density limits for this deck                             |

## Slide options

| Option                | Values                                                                                                    | Effect                               |
| --------------------- | --------------------------------------------------------------------------------------------------------- | ------------------------------------ |
| `layout`              | `default`, `center`, `cover`, `section`, `grid`, `columns`, `split`, `image`, `image-left`, `image-right` | see [Layouts](/formats/deck/layouts) |
| `cols`                | `1` – `4`                                                                                                 | grid columns                         |
| `ratio`               | `1:1`, `2:1`…                                                                                             | column proportions                   |
| `image`, `alt`, `fit` | path, text, `cover` / `contain`                                                                           | image layouts                        |
| `overlay`             | `0` – `1`                                                                                                 | darkening of the background image    |
| `transition`          | `slide`, `fade`, `none`                                                                                   | transition to this slide             |
| `bg`                  | CSS color                                                                                                 | slide background                     |
| `footer`              | `true`, `false`                                                                                           | forces or hides the footer           |
| `id`, `title`         | text                                                                                                      | identifier, title in search results  |

Unknown values produce a diagnostic with the line number.