Nuxt's [configuration](/docs/api/configuration/nuxt-config) and [hooks](/docs/guide/going-further/hooks) systems make it possible to customize every aspect of Nuxt and add any integration you might need (Vue plugins, CMS, server routes, components, logging, etc.).
**Nuxt Modules** are functions that sequentially run when starting Nuxt in development mode using `nuxi dev` or building a project for production with `nuxi build`.
With modules, you can encapsulate, properly test, and share custom solutions as npm packages without adding unnecessary boilerplate to your project, or requiring changes to Nuxt itself.
2. Install dependencies using your favorite package manager
3. Prepare local files for development using `npm run dev:prepare`
4. Follow this document to learn more about Nuxt Modules
### Using the Starter
Learn how to perform basic tasks with the module starter.
#### How to Develop
While your module source code lives inside the `src` directory, in most cases, to develop a module, you need a Nuxt application. That's what the `playground` directory is about. It's a Nuxt application you can tinker with that is already configured to run with your module.
You can interact with the playground like with any Nuxt application.
- Launch its development server with `npm run dev`, it should reload itself as you make changes to your module in the `src` directory
- Build it with `npm run dev:build`
::alert{type=info}
All other `nuxi` commands can be used against the `playground` directory (e.g. `nuxi <COMMAND> playground`). Feel free to declare additional `dev:*` scripts within your `package.json` referencing them for convenience.
::
#### How to Test
The module starter comes with a basic test suite:
- A linter powered by [ESLint](https://eslint.org), run it with `npm run lint`
- A test runner powered by [Vitest](https://vitest.dev), run it with `npm run test` or `npm run test:watch`
::alert{type=info}
Feel free to augment this default test strategy to better suit your needs.
::
#### How to Build
Nuxt Modules come with their own builder provided by [`@nuxt/module-builder`](https://github.com/nuxt/module-builder#readme). This builder doesn't require any configuration on your end, supports TypeScript, and makes sure your assets are properly bundled to be distributed to other Nuxt applications.
You can build your module by running `npm run prepack`.
While building your module can be useful in some cases, most of the time you won't need to build it on your own: the `playground` takes care of it while developing, and the release script also has you covered when publishing.
Before publishing your module to npm, makes sure you have an [npmjs.com](https://www.npmjs.com) account and that you're authenticated to it locally with `npm login`.
::
While you can publish your module by bumping its version and using the `npm publish` command, the module starter comes with a release script that helps you make sure you publish a working version of your module to npm and more.
To use the release script, first, commit all your changes (we recommend you follow [Conventional Commits](https://www.conventionalcommits.org/en/v1.0.0) to also take advantage of automatic version bump and changelog update), then run the release script with `npm run release`.
When running the release script, the following will happen:
- First, it will run your test suite by:
- Running the linter (`npm run lint`)
- Running unit, integration, and e2e tests (`npm run test`)
- Building the module (`npm run prepack`)
- Then, if your test suite went well, it will proceed to publish your module by:
- Bumping your module version and generating a changelog according to your Conventional Commits
- Publishing the module to npm (for that purpose, the module will be built again to ensure its updated version number is taken into account in the published artifact)
- Pushing a git tag representing the newly published version to your git remote origin
::alert{type=info}
As with other scripts, feel free to fine-tune the default `release` script in your `package.json` to better suit your need.
::
## Developing Modules
Nuxt Modules come with a variety of powerful APIs and patterns allowing them to alter a Nuxt application in pretty much any way possible. This section teaches you how to take advantage of those.
- published modules are distributed on npm - you can see a list of some community modules on [the Nuxt website](/modules).
- "local" modules, they exist within a Nuxt project itself, either [inlined in Nuxt config](/docs/api/configuration/nuxt-config#modules) or as part of [the `modules` directory](/docs/guide/directory-structure/modules).
In either case, their anatomy is similar.
#### Module Definition
::alert{type=info}
When using the starter, your module definition is available at `src/module.ts`.
::
The module definition is the entry point of your module. It's what gets loaded by Nuxt when your module is referenced within a Nuxt configuration.
At a low level, a Nuxt Module definition is a simple, potentially asynchronous, function accepting inline user options and a `nuxt` object to interact with Nuxt.
However, **we do not recommend** using this low-level function definition. Instead, to define a module, **we recommend** using the object-syntax with `meta` property to identify your module, especially when publishing to npm.
This helper makes writing Nuxt Module more straightforward by implementing many common patterns seen in modules, guaranteeing future compatibility, and improving your module author developer experience and the one of your module users.
Ultimately `defineNuxtModule` returns a wrapper function with the lower level `(inlineOptions, nuxt)` module signature. This wrapper function applies defaults and other necessary steps before calling your `setup` function:
Modules, like everything in a Nuxt configuration, aren't included in your application runtime. However, you might want your module to provide, or inject runtime code to the application it's installed on. That's what the runtime directory enables you to do.
Published modules cannot leverage auto-imports for assets within their runtime directory. Instead, they have to import them explicitly from `#imports` or alike.
Indeed, auto-imports are not enabled for files within `node_modules` (the location where a published module will eventually live) for performance reasons. That's why the module starter [deliberately disables them](https://github.com/nuxt/starter/blob/module/.nuxtrc#L1) while developing a module.
[Nuxt Module Builder](https://github.com/nuxt/module-builder#readme) is a zero-configuration build tool taking care of all the heavy lifting to build and ship your module. It ensures proper compatibility of your module build artifact with Nuxt applications.
[Nuxt Kit](/docs/guide/going-further/kit) provides composable utilities to help your module interact with Nuxt applications. It's recommended to use Nuxt Kit utilities over manual alternatives whenever possible to ensure better compatibility and code readability of your module.
Because modules aren't part of the application runtime, their options aren't either. However, in many cases, you might need access to some of these module options within your runtime code. We recommend exposing the needed config using Nuxt's [`runtimeConfig`](/docs/api/configuration/nuxt-config#runtimeconfig).
Be careful not to expose any sensitive module configuration on the public runtime config, such as private API keys, as they will end up in the public bundle.
If your module should provide other kinds of assets, they can also be injected. Here's a simple example module injecting a stylesheet through Nuxt's `css` array.
```js
import { defineNuxtModule, addPlugin, createResolver } from '@nuxt/kit'
If your module depends on other modules, you can add them by using Nuxt Kit's `installModule` utility. For example, if you wanted to use Nuxt Tailwind in your module, you could add it as below:
```ts
import { defineNuxtModule, createResolver, installModule } from '@nuxt/kit'
[Lifecycle hooks](/docs/guide/going-further/hooks) allow you to expand almost every aspect of Nuxt. Modules can hook to them programmatically or through the `hooks` map in their definition.
```js
import { defineNuxtModule, addPlugin, createResolver } from '@nuxt/kit'
export default defineNuxtModule({
// Hook to the `app:error` hook through the `hooks` map
Testing helps ensuring your module works as expected given various setup. Find in this section how to perform various kinds of tests against your module.
#### Unit and Integration
::alert{type=info}
We're still discussing and exploring how to ease unit and integration testing on Nuxt Modules.
[Check out this RFC to join the conversation](https://github.com/nuxt/nuxt/discussions/18399).
::
#### End to End
[Nuxt Test Utils](/docs/getting-started/testing) is the go-to library to help you test your module in an end-to-end way. Here's the workflow to adopt with it:
1. Create a Nuxt application to be used as a "fixture" inside `test/fixtures/*`
2. Setup Nuxt with this fixture inside your test file
3. Interact with the fixture using utilities from `@nuxt/test-utils` (e.g. fetching a page)
4. Perform checks related to this fixture (e.g. "HTML contains ...")
5. Repeat
In practice, the fixture:
```js [test/fixtures/ssr/nuxt.config.ts]
// 1. Create a Nuxt application to be used as a "fixture"
import MyModule from '../../../src/module'
export default defineNuxtConfig({
ssr: true,
modules: [
MyModule
]
})
```
And its test:
```js [test/rendering.ts]
import { describe, it, expect } from 'vitest'
import { fileURLToPath } from 'node:url'
import { setup, $fetch } from '@nuxt/test-utils'
describe('ssr', async () => {
// 2. Setup Nuxt with this fixture inside your test file
// 3. Interact with the fixture using utilities from `@nuxt/test-utils`
const html = await $fetch('/')
// 4. Perform checks related to this fixture
expect(html).toContain('<div>ssr</div>')
})
})
// 5. Repeat
describe('csr', async () => { /* ... */ })
```
::alert{type=info}
An example of such a workflow is available on [the module starter](https://github.com/nuxt/starter/blob/module/test/basic.test.ts).
::
#### Manual QA With Playground and Externally
Having a playground Nuxt application to test your module when developing it is really useful. [The module starter integrates one for that purpose](#how-to-develop).
You can test your module with other Nuxt applications (applications that are not part of your module repository) locally. To do so, you can use [`npm pack`](https://docs.npmjs.com/cli/commands/npm-pack) command, or your package manager equivalent, to create a tarball from your module. Then in your test project, you can add your module to `package.json` packages as: `"my-module": "file:/path/to/tarball.tgz"`.
After that, you should be able to reference `my-module` like in any regular project.
### Best Practices
With great power comes great responsibility. While modules are powerful, here are some best practices to keep in mind while authoring modules to keep applications performant and developer experience great.
#### Async Modules
As we've seen, Nuxt Modules can be asynchronous. For example, you may want to develop a module that needs fetching some API or calling an async function.
However, be careful with asynchronous behaviors as Nuxt will wait for your module to setup before going to the next module and starting the development server, build process, etc. Prefer deferring time-consuming logic to Nuxt hooks.
::alert{type="warning"}
If your module takes more than **1 second** to setup, Nuxt will emit a warning about it.
::
#### Always Prefix Exposed Interfaces
Nuxt Modules should provide an explicit prefix for any exposed configuration, plugin, API, composable, or component to avoid conflict with other modules and internals.
Ideally, you should prefix them with your module's name (e.g. if your module is called `nuxt-foo`, expose `<FooButton>` and `useFooBar()` and **not**`<Button>` and `useBar()`).
#### Be TypeScript Friendly
Nuxt 3, has first-class TypeScript integration for the best developer experience.
Exposing types and using TypeScript to develop modules benefits users even when not using TypeScript directly.
#### Avoid CommonJS Syntax
Nuxt 3, relies on native ESM. Please read [Native ES Modules](/docs/guide/concepts/esm) for more information.
#### Document Module Usage
Consider documenting module usage in the readme file:
- Why use this module?
- How to use this module?
- What does this module do?
Linking to the integration website and documentation is always a good idea.
This not only provides potential users of your module a quick and easy way to experiment with the module but also an easy way for them to build minimal reproductions they can send you when they encounter issues.
Nuxt 3, Nuxt Kit, and other new toolings are made to have both forward and backward compatibility in mind.
Please use "X for Nuxt" instead of "X for Nuxt 3" to avoid fragmentation in the ecosystem and prefer using `meta.compatibility` to set Nuxt version constraints.
#### Stick With Starter Defaults
The module starter comes with a default set of tools and configurations (e.g. ESLint configuration). If you plan on open-sourcing your module, sticking with those defaults ensures your module shares a consistent coding style with other [community modules](/modules) out there, making it easier for others to contribute.
## Ecosystem
[Nuxt Module ecosystem](/modules) represents more than 15 million monthly NPM downloads and provides extended functionalities and integrations with all sort of tools. You can be part of this ecosystem!
### Module Types
**Official modules** are modules prefixed (scoped) with `@nuxt/` (e.g. [`@nuxt/content`](https://content.nuxtjs.org)). They are made and maintained actively by the Nuxt team. Like with the framework, contributions from the community are more than welcome to help make them better!
**Community modules** are modules prefixed (scoped) with `@nuxtjs/` (e.g. [`@nuxtjs/tailwindcss`](https://tailwindcss.nuxtjs.org)). They are proven modules made and maintained by community members. Again, contributions are welcome from anyone.
**Third party and other community modules** are modules (often) prefixed with `nuxt-`. Anyone can make them, using this prefix allows these modules to be discoverable on npm. This is the best starting point to draft and try an idea!
**Private or personal modules** are modules made for your own use case or company. They don't need to follow any naming rules to work with Nuxt and are often seen scoped under an npm organization (e.g. `@my-company/nuxt-auth`)
Any community modules are welcome to be listed on [the module list](/modules). To be listed, [open an issue in the nuxt/modules](https://github.com/nuxt/modules/issues/new?template=module_request.yml) repository. The Nuxt team can help you to apply best practices before listing.
By moving your modules to [nuxt-modules](https://github.com/nuxt-modules), there is always someone else to help, and this way, we can join forces to make one perfect solution.
If you have an already published and working module, and want to transfer it to `nuxt-modules`, [open an issue in nuxt/modules](https://github.com/nuxt/modules/issues/new).
By joining `nuxt-modules` we can rename your community module under the `@nuxtjs/` scope and provide a subdomain (e.g. `my-module.nuxtjs.org`) for its documentation.
<!-- ## Module Internals
Maybe just a quick section touching on "how modules work" under the hood, priority, etc. -->