> For the complete documentation index, see [llms.txt](https://docs.chord.co/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.chord.co/chord-oms/shopify/developer-tools/gatsby/sdk-reference.md).

# SDK Reference

The Chord client-side Javascript SDK is installed as a Gatsby theme. It's available as an npm package, `@chordcommerce/gatsby-theme-performance`, via GitHub Packages.

Despite the name, this package does not provide a visual theme. To quote from the [Gatsby documentation](https://www.gatsbyjs.com/docs/themes/what-are-gatsby-themes/):

{% hint style="info" %}
Gatsby themes are plugins that include a `gatsby-config.js` file and add pre-configured functionality, data sourcing, and/or UI code to Gatsby sites. You can think of Gatsby themes as separate Gatsby sites that can be put together and allow you to split up a larger Gatsby project!
{% endhint %}

The `gatsby-theme-performance` theme includes the Chord SDK, a set of methods you can import and use in your React components to do things like add items to a cart and check out. The theme also pre-configures your Gatsby site with a number of useful commerce features like product feeds and internationalization support.

The Chord SDK is available to use in your React components via React hooks:

| Hook                                                                                    | Description                                                                                           |
| --------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------- |
| [useAnalytics](/chord-oms/shopify/developer-tools/gatsby/sdk-reference/useanalytics.md) | Provides support for sending UI-related tracking events to Segment.                                   |
| [useAuth](/chord-oms/shopify/developer-tools/gatsby/sdk-reference/useauth.md)           | Provides support for user authentication with a Shopify customer account.                             |
| [useCart](/chord-oms/shopify/developer-tools/gatsby/sdk-reference/usecart.md)           | Returns the current shopping cart, and functions for creating and interacting with the shopping cart. |
| [useUser](/chord-oms/shopify/developer-tools/gatsby/sdk-reference/useuser.md)           | Returns the current user, and functions for loading data about the user.                              |


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