---
id: node
title: Node.js
---
## Installation
### npm
Install with `npm`:

```bash
npm install katex
# or globally
npm install -g katex
```

### Yarn
Install with `Yarn`:

```bash
yarn add katex
# or globally
yarn global add katex
```

### Building from Source
To build you will need Git, Node.js 10 or later, and Yarn.

Clone a copy of the GitHub source repository:
```bash
git clone https://github.com/KaTeX/KaTeX.git
cd KaTeX
```

Then install dependencies and run `build` script:
```bash
yarn
yarn build
```

It will automatically transpile code and include only necessary fonts for
target environments specified by [Browserslist config](https://github.com/browserslist/browserslist#environment-variables).
For example, if you are making a web app for a kiosk with Chrome 68, run
`BROWSERSLIST="Chrome 68" yarn build` and it will produce build with no
transpilation, as it fully supports ES6, and only include WOFF2 fonts.

You can override included fonts using environment variables. Set `USE_(FONT NAME)`
environment variable to `"true"` or `"false"`, to force a font type to be included
or excluded, respectively.`

If you'd like to use the built KaTeX in other projects, install the package by
specifying the path:
```bash
yarn add /path/to/KaTeX
# or using npm
npm install /path/to/KaTeX
```

> You can manually download the package and source code from
[GitHub releases](https://github.com/KaTeX/KaTeX/releases).

## Importing
KaTeX is exported as a CommonJS module, which can be imported using `require`:
```js
const katex = require('katex');
```

KaTeX also conditionally exports an ECMAScript module:
```js
import katex from 'katex';
```

> The ES module contains ES6 syntaxes and features, and may need transpiling to
use in old environments.

See the [API](api.html) for available functions in the `katex` module.

## Including in webpages

To render any HTML generated by e.g. `katex.renderToString`, you will
still need to link the CSS file, make the KaTeX font files available to the
client, and use the HTML5 doctype.  See [browser usage](browser.html).
Note, however, that you do not need to include `katex.js` on the client.

## Using mhchem extension

The [mhchem extension](https://github.com/KaTeX/KaTeX/tree/main/contrib/mhchem)
adds its features by modifying the `katex` module.  So you can use KaTeX with
mhchem in Node as follows:

```js
const katex = require('katex');
require('katex/contrib/mhchem'); // modify katex module
const html = katex.renderToString('\\ce{CO2 + C -> 2 C0}');
```
