# Overriding Components

Starlight’s default UI and configuration options are designed to be flexible and work for a range of content. Much of Starlight's default appearance can be customized with [CSS](/guides/guides-css-and-tailwind) and [configuration options](/guides/guides-customization).

When you need more than what’s possible out of the box, Starlight supports building your own custom components to extend or override (completely replace) its default components.

## When to override

Overriding Starlight’s default components can be useful when:

- You want to change how a part of Starlight’s UI looks in a way not possible with [custom CSS](/guides/guides-css-and-tailwind).
- You want to change how a part of Starlight’s UI behaves.
- You want to add some additional UI alongside Starlight’s existing UI.

## How to override

:::::steps
::::step
Choose the Starlight component you want to override.
You can find a full list of components in the [Overrides Reference](/guides/reference-overrides).

:::callout{intent="tip"}
Not sure which component you need to override? Use the [interactive Starlight Overrides Map](https://starlight-overrides-map.netlify.app/) to discover the names of Starlight's UI components.
:::

This example will override Starlight’s [`SocialIcons`](/guides/reference-overrides#socialicons) component in the page nav bar.
::::

:::step
Create an Astro component to replace the Starlight component with.
This example renders a contact link.

```astro
---
// src/components/EmailLink.astro

const email = 'houston@example.com';
---

<a href=`mailto:${email}`>E-mail Me</a>
```
:::

:::step
Tell Starlight to use your custom component in the [`components`](/guides/reference-configuration#components) configuration option in `astro.config.mjs`:

```js {9-12}
// astro.config.mjs
import { defineConfig } from 'astro/config';
import starlight from '@astrojs/starlight';

export default defineConfig({
	integrations: [
		starlight({
			title: 'My Docs with Overrides',
			components: {
				// Override the default `SocialIcons` component.
				SocialIcons: './src/components/EmailLink.astro',
			},
		}),
	],
});
```
:::
:::::

## Reuse a built-in component

You can build with Starlight’s default UI components just as you would with your own: importing and rendering them in your own custom components. This allows you to keep all of Starlight's basic UI within your design, while adding extra UI alongside them.

The example below shows a custom component that renders an e-mail link along with the default `SocialIcons` component:

```astro {3,7}
---
// src/components/EmailLink.astro
import Default from '@astrojs/starlight/components/SocialIcons.astro';
---

<a href="mailto:houston@example.com">E-mail Me</a>
<Default><slot /></Default>
```

When rendering a built-in component inside a custom component add a [`<slot />`](https://docs.astro.build/en/basics/astro-components/#slots) inside the default component. This makes sure that if the component is passed any child elements, Astro knows where to render them.

If you are reusing the [`PageFrame`](/guides/reference-overrides#pageframe) or [`TwoColumnContent`](/guides/reference-overrides#twocolumncontent) components which contain [named slots](https://docs.astro.build/en/basics/astro-components/#named-slots), you also need to [transfer](https://docs.astro.build/en/basics/astro-components/#transferring-slots) these slots as well.

The example below shows a custom component that reuses the `TwoColumnContent` component which contains an additional `right-sidebar` named slot that needs to be transferred:

```astro {8}
---
// src/components/CustomContent.astro
import Default from '@astrojs/starlight/components/TwoColumnContent.astro';
---

<Default>
	<slot />
	<slot name="right-sidebar" slot="right-sidebar" />
</Default>
```

## Use page data

When overriding a Starlight component, you can access the global [`starlightRoute` object](/guides/guides-route-data) containing all the data for the current page.
This allows you to use these values to control how your component template renders.

In the following example, a replacement [`PageTitle`](/guides/reference-overrides#pagetitle) component displays the current page’s title as set in the content’s frontmatter:

```astro {4} "{title}"
---
// src/components/Title.astro

const { title } = Astro.locals.starlightRoute.entry.data;
---

<h1 id="_top">{title}</h1>

<style>
	h1 {
		font-family: 'Comic Sans';
	}
</style>
```

Learn more about all the available properties in the [Route Data Reference](/guides/reference-route-data).

### Only override on specific pages

Component overrides apply to all pages. However, you can conditionally render using values from `starlightRoute` to determine when to show your custom UI, when to show Starlight’s default UI, or even when to show something entirely different.

In the following example, a component overriding Starlight's [`Footer`](/guides/reference-overrides#footer-1) displays "Built with Starlight 🌟" on the homepage only, and otherwise shows the default footer on all other pages:

```astro
---
// src/components/ConditionalFooter.astro
import Default from '@astrojs/starlight/components/Footer.astro';

const isHomepage = Astro.locals.starlightRoute.id === '';
---

{
	isHomepage ? (
		<footer>Built with Starlight 🌟</footer>
	) : (
		<Default>
			<slot />
		</Default>
	)
}
```

Learn more about conditional rendering in [Astro’s Template Syntax guide](https://docs.astro.build/en/basics/astro-syntax/#dynamic-html).

## Related pages

- [Starlight](../index.md)
- [Using Components](./components-using-components.md)
- [Pages](./guides-pages.md)
- [Not found](./more-404.md)
- [Configuration Reference](./reference-configuration.md)
- [Plugins and Integrations](./resources-plugins.md)
- [Start Here](./start-here-index.md)
- [Getting Started](./start-here-getting-started.md)
- [Cards](./components-cards.md)
- [Guides](./guides-index.md)

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