> For the complete documentation index, see [llms.txt](https://docs.hatsprotocol.xyz/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.hatsprotocol.xyz/for-developers/hats-modules/modules-sdk.md).

# Modules SDK

## Overview

The Modules SDK is an open source JavaScript client that provides core functionality for using **existing** [eligibility](/for-developers/hats-protocol-for-developers/eligibility-modules.md), [toggle](/for-developers/hats-protocol-for-developers/toggle-modules.md) and [hatter](/for-developers/hats-protocol-for-developers/hat-admins-and-hatter-contracts.md#hatter-contracts) Modules and is designed to work both in the browser and in Node.js.

The available Modules are included in the [Modules registry](/for-developers/hats-modules/building-hats-modules/modules-registry.md) - an open source registry (currently hosted on GitHub) which contains the various Hats Modules which are available to use.

For documentation about creating new Hats Modules, click [here](/for-developers/hats-modules/building-hats-modules.md).

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[Getting Started](/for-developers/hats-modules/modules-sdk/getting-started.md)
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[Get Available Modules](/for-developers/hats-modules/modules-sdk/get-available-modules.md)
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[Create New Instance/s](/for-developers/hats-modules/modules-sdk/create-new-instance-s.md)
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[Composing Modules](/for-developers/hats-modules/modules-sdk/composing-modules.md)
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[Interact With Instances](/for-developers/hats-modules/modules-sdk/interact-with-instances.md)
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[Utilities](/for-developers/hats-modules/modules-sdk/utilities.md)
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[Types](/for-developers/hats-modules/modules-sdk/types.md)
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