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astro/docs/guides/markdown-content.md
Pavel Mineev d3969436dc
Remark and rehype plugins (#562)
* remark plugins

* remove unused dependency

* enable codeblocks

* backward compatibility with remark-code-titles

* add support for rehype plugins

* add proper types for plugins

* fixes after review

- connect plugins by name
- make plugins configurable
- connect gfm and footnotes if no plugins provided from config
- add more plugins to example

* update and rename example

* add documentation for markdown plugins

* chore: rename with-markdown-plugins example

* chore: restructure dependencies

* feat: add back smartypants, fix mdx expressions

* chore: remove log

* test: add markdown plugin tests

* chore: add changeset

* docs: update markdown doc

Co-authored-by: Nate Moore <nate@skypack.dev>
2021-07-01 11:55:22 -05:00

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Markdown

---
layout: ~/layouts/Main.astro
title: Markdown Content
---
Astro comes with out-of-the-box Markdown support powered by the expansive [remark](https://remark.js.org/) ecosystem.
## Remark and Rehype Plugins
In addition to [custom components inside the `<Markdown>` component](#markdown-component), Astro comes with [GitHub-flavored Markdown](https://github.github.com/gfm/) support, [Footnotes](https://github.com/remarkjs/remark-footnotes) syntax, [Smartypants](https://github.com/silvenon/remark-smartypants), and syntax highlighting via [Prism](https://prismjs.com/) pre-enabled.
Also, Astro supports third-party plugins for Markdown. You can provide your plugins in `astro.config.mjs`.
> **Note** Enabling custom `remarkPlugins` or `rehypePlugins` removes Astro's built-in support for [GitHub-flavored Markdown](https://github.github.com/gfm/) support, [Footnotes](https://github.com/remarkjs/remark-footnotes) syntax, [Smartypants](https://github.com/silvenon/remark-smartypants). You must explicitly add these plugins to your `astro.config.mjs` file, if desired.
## Add a markdown plugin in Astro
If you want to add a plugin, you need to install the npm package dependency in your project and then update the `markdownOptions.remarkPlugins` or `markdownOptions.rehypePlugins` depends on what plugin you want to have:
```js
// astro.config.js
export default {
markdownOptions: {
remarkPlugins: [
// Add a Remark plugin that you want to enable for your project.
// If you need to provide options for the plugin, you can use an array and put the options as the second item.
// 'remark-slug',
// ['remark-autolink-headings', { behavior: 'prepend'}],
]
rehypePlugins: [
// Add a Rehype plugin that you want to enable for your project.
// If you need to provide options for the plugin, you can use an array and put the options as the second item.
// 'rehype-slug',
// ['rehype-autolink-headings', { behavior: 'prepend'}],
]
},
};
```
You can provide names of the plugins as well as import them:
```js
// astro.config.js
export default {
markdownOptions: {
remarkPlugins: [
import('remark-slug'),
[import('remark-autolink-headings'), { behavior: 'prepend' }],
],
},
};
```
### Markdown Pages
Astro treats any `.md` files inside of the `/src/pages` directory as pages. These pages are processed as plain markdown files and do not support components. If you're looking to embed rich components in your markdown, take a look at the [Markdown Component](#astros-markdown-component) section.
`layout`
The only special Frontmatter key is `layout`, which defines the relative path to an `.astro` component which should wrap your Markdown content.
`src/pages/index.md`
```jsx
---
layout: ../layouts/main.astro
---
# Hello World!
```
Layout files are normal `.astro` components. Any Frontmatter defined in your `.md` page will be exposed to the Layout component as the `content` prop. `content` also has an `astro` key which holds special metadata about your file, like the complete Markdown `source` and a `headings` object.
Keep in mind that the only guaranteed variables coming from the `content` prop object are `astro` and `url`. An example of what a blog post `content` object might look like is as follows:
```json
{
/** Frontmatter from blog post
"title": "",
"date": "",
"author": "",
"description": "",
**/
"astro": {
"headers": [],
"source": ""
},
"url": ""
}
```
The rendered Markdown content is placed into the default `<slot />` element.
`src/layouts/main.astro`
```jsx
---
const { content } = Astro.props;
---
<html>
<head>
<title>{content.title}</title>
</head>
<body>
<slot/>
</body>
</html>
```
### Astro's Markdown Component
Astro has a dedicated component used to let you render your markdown as HTML components. This is a special component that is only exposed to `.astro` files. To use the `<Markdown>` component, within yout frontmatter block use the following import statement:
```jsx
---
import { Markdown } from 'astro/components';
---
```
You can utilize this within your `.astro` file by doing the following:
```jsx
---
import { Markdown } from 'astro/components';
---
<Layout>
<Markdown>
# Hello world!
The contents inside here is all in markdown.
</Markdown>
</Layout>
```
`<Markdown>` components provide more flexibility and allow you to use plain HTML or custom components. For example:
````jsx
---
// For now, this import _must_ be named "Markdown" and _must not_ be wrapped with a custom component
// We're working on easing these restrictions!
import { Markdown } from 'astro/components';
import Layout from '../layouts/main.astro';
import MyFancyCodePreview from '../components/MyFancyCodePreview.tsx';
const expressions = 'Lorem ipsum';
---
<Layout>
<Markdown>
# Hello world!
**Everything** supported in a `.md` file is also supported here!
There is _zero_ runtime overhead.
In addition, Astro supports:
- Astro {expressions}
- Automatic indentation normalization
- Automatic escaping of expressions inside code blocks
```jsx
// This content is not transformed!
const object = { someOtherValue };
```
- Rich component support like any `.astro` file!
- Recursive Markdown support (Component children are also processed as Markdown)
<MyFancyCodePreview:visible>
```jsx
const object = { someOtherValue };
```
</MyFancyCodePreview:visible>
</Markdown>
</Layout>
````
### Remote Markdown
If you have Markdown in a remote source, you may pass it directly to the Markdown component through the `content` attribute. For example, the example below fetches the README from Snowpack's Github repository and renders it as HTML.
```jsx
---
import { Markdown } from 'astro/components';
const content = await fetch('https://raw.githubusercontent.com/snowpackjs/snowpack/main/README.md').then(res => res.text());
---
<Layout>
<Markdown content={content} />
</Layout>
```
There might be times when you want to combine both dynamic, and static markdown. If that is the case, you can nest `<Markdown>` components with each other to get the best of both worlds.
```jsx
---
import { Markdown } from 'astro/components';
const content = await fetch('https://raw.githubusercontent.com/snowpackjs/snowpack/main/README.md').then(res => res.text());
---
<Layout>
<Markdown>
## Markdown example
Here we have some __Markdown__ code. We can also dynamically render content from remote places.
<Markdown content={content} />
</Mardown>
</Layout>
```
### Security FAQs
**Aren't there security concerns to rendering remote markdown directly to HTML?**
Yes! Just like with regular HTML, improper use of the `Markdown` component can open you up to a [cross-site scripting (XSS)](https://en.wikipedia.org/wiki/Cross-site_scripting) attack. If you are rendering untrusted content, be sure to _sanitize your content **before** rendering it_.
**Why not use a prop like React's `dangerouslySetInnerHTML={{ __html: content }}`?**
Rendering a string of HTML (or Markdown) is an extremely common use case when rendering a static site and you probably don't need the extra hoops to jump through. Rendering untrusted content is always dangerous! Be sure to _sanitize your content **before** rendering it_.