---
title: "Syntax"
description: "Exact syntax rules for Deckup pages, layouts, themes, and named slots in Astro and MDX."
---

> Documentation Index
> Fetch the complete documentation index at: https://deckup.yuku.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Syntax

## Deck files

A deck is one `.astro` or `.mdx` file.
Both formats produce an ordered list of pages and use the same theme layout system.

## Astro pages

Astro decks import `Page` and contain only top-level `<Page>` components:

```astro
---
import Page from "@deckup/astro/page";
---

<Page title="Presentation title" layout="cover">
  <h1>Presentation title</h1>
</Page>

<Page title="Content">
  <p>Slide content</p>
</Page>
```

## MDX pages

Horizontal rules split MDX decks into pages:

```mdx
# Cover title

Cover subtitle

---

# Content slide

- First point
- Second point
```

Deckup wraps each segment in a generated `Page` component.
Empty pages are invalid, so do not use adjacent rules or a trailing rule without content.

## Layout declarations

Deckup assigns `cover` to page 1 and `default` to every later page unless the page declares another layout.

In Astro, set `layout` directly on `Page`:

```astro
<Page title="Two columns" layout="two-column">
  <h1>Two columns</h1>
</Page>
```

The value must be a static, non-empty string.
Expressions and shorthand attributes are invalid, and a `Page` may not declare multiple `layout` attributes.
When using a JSX spread, place it before `layout`; a spread after the explicit layout is rejected because it could overwrite the analyzed value at runtime.

In MDX, declare the layout with an import-free `PageMeta` marker:

```mdx
<PageMeta layout="two-column" />
```

`PageMeta` is an import-free Deckup marker, not a runtime component.
A page may contain at most one `PageMeta` declaration.
It must be the first meaningful direct child; whitespace and non-rendering comments may precede it.
The marker must be self-closing and may contain exactly one static, non-empty `layout` string attribute. Expressions, spreads, unknown attributes, children, and paired tags are invalid.
`PageMeta` is reserved and is removed before content renders.
Layout IDs start with a lowercase letter and contain only lowercase letters, numbers, and hyphens.

## Named slots

Target a named region with Astro's standard `slot` attribute:

```astro
<Page title="Two columns" layout="two-column">
  <h1>Two columns</h1>
  <p slot="left">Left side</p>
  <p slot="right">Right side</p>
</Page>
```

The same syntax works on JSX elements in MDX.
Available layout IDs and slot names depend on the selected theme.

## Deck-level themes

In MDX, set static theme metadata in YAML frontmatter:

```mdx
---
title: Product update
theme: minimal
---
```

In Astro, declare a static top-level constant in the frontmatter script:

```astro
---
const theme = "minimal";
---
```

The value must be a static string.
Theme precedence is deck metadata, then `deckup.config.*`, then `default`.

Source: https://deckup.yuku.dev/references/syntax/index.mdx