# Code Highlighting

`nextra-theme-docs` uses [Prism](https://prismjs.com) and [prism-react-renderer](https://github.com/FormidableLabs/prism-react-renderer) 
to highlight the code blocks. This section covers how you can customize it.

## More Languages

To keep the bundle small, only a [subset of languages](https://github.com/FormidableLabs/prism-react-renderer/blob/master/src/vendor/prism/includeLangs.js)
are included in the syntax highlighter. If you want to add more languages, you can do the following:

1. Run `yarn add prismjs prism-react-renderer` to add dependencies to your Nextra project.
2. Add the following code to your `pages/_app.js`:

```jsx
import Prism from 'prism-react-renderer/prism'

(typeof global !== "undefined" ? global : window).Prism = Prism

require("prismjs/components/prism-kotlin")
require("prismjs/components/prism-csharp")
```

Restart your app and you will have Kotlin and C# code highlighting supported. 
You can find the full list of available languages [here](https://github.com/PrismJS/prism/tree/master/components).

{/*## Custom Themes*/}