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---

title: Frontend-only SDK description: A reference for implementing a frontend-only Clerk SDK

While ClerkJS can be used in any browser context and framework, realistically users expect to consume its features through the conventions and syntax of their framework of choice. For example, @clerk/clerk-react turns ClerkJS into React components, @clerk/astro into Astro components, and so on.

In non-browser environments, you’ll need to re-implement the Clerk class in the SDK’s programming language, interacting with the FAPI.

Expected features

• User only needs to provide their Publishable Key
• User only needs to adjust one or two files to add Clerk to their app (e.g. adding Clerk to the configuration file of that framework)
• User can use Clerk’s components in their choice of framework (e.g. in a React-based framework you import these components as React components)
• Give users access to Client{{ target: '_blank' }}, Session{{ target: '_blank' }}, User{{ target: '_blank' }}, and Organization{{ target: '_blank' }} properties through the framework’s choice of state management
• User should be able to use ClerkJS options{{ target: '_blank' }}

Implementation

While the implementation details will vary for each SDK, there are certain steps you'll have to go through in any case. Consider the steps below a rough guidance on what needs to be done, and also remember to follow the conventions.

[!NOTE] The code blocks below will be written in pseudo-code. If you're looking for real-world examples, have a look at these repositories: @clerk/clerk-react, @clerk/astro

<Steps> ### Create a Clerk instance

Create a Clerk instance that will only be invoked once (e.g. following the singleton pattern). During its initialization you'll execute the following steps.

import { runOnce } from './utils'
// States accessible to other parts of your SDK and/or its users
import { $clerk, $state } from './stores'

export const createClerkInstance = runOnce(createClerkInstanceInternal)

async function createClerkInstanceInternal(options) {
  let clerkJSInstance = window.Clerk
}

Hotload ClerkJS

In order to make Clerk available on the window object, your SDK needs to load ClerkJS. Call loadClerkJsScript() from @clerk/shared.

import { loadClerkJSScript } from '@clerk/shared/loadClerkJSScript'
import { runOnce } from './utils'
import { $clerk, $state } from './stores'

export const createClerkInstance = runOnce(createClerkInstanceInternal)

async function createClerkInstanceInternal(options) {
  let clerkJSInstance = window.Clerk

  if (!clerkJSInstance) {
    await loadClerkJSScript(options)

    if (!window.Clerk) {
      throw new Error('Failed to download latest ClerkJS.')
    }
    clerkJSInstance = window.Clerk
  }

  if (!$clerk.get()) {
    $clerk.set(clerkJSInstance)
  }
}

Call window.Clerk.load()

By calling window.Clerk.load() the Clerk class is initialized and your SDK now has access to all its functionality.

import { loadClerkJSScript } from '@clerk/shared/loadClerkJSScript'
import { runOnce } from './utils'
import { $clerk, $state } from './stores'

export const createClerkInstance = runOnce(createClerkInstanceInternal)

async function createClerkInstanceInternal(options) {
  let clerkJSInstance = window.Clerk

  if (!clerkJSInstance) {
    // loadClerkJSScript() codepath
  }

  if (!$clerk.get()) {
    $clerk.set(clerkJSInstance)
  }

  await clerkJSInstance.load(options)
}

Add event listeners

Expose properties to the internal state (e.g. a useState in React) through adding event listeners.

import { loadClerkJSScript } from '@clerk/shared/loadClerkJSScript'
import { runOnce } from './utils'
import { $clerk, $state } from './stores'

export const createClerkInstance = runOnce(createClerkInstanceInternal)

async function createClerkInstanceInternal(options) {
  let clerkJSInstance = window.Clerk

  if (!clerkJSInstance) {
    // loadClerkJSScript() codepath
  }

  await clerkJSInstance.load(options)

  if (!$clerk.get()) {
    $clerk.set(clerkJSInstance)
  }

  clerkJSInstance.addListener((resources) => {
    $state.setKey('client', resources.client)
    $state.setKey('session', resources.session)
    $state.setKey('user', resources.user)
    $state.setKey('organization', resources.organization)
  })
}

Add UI components

Build out the components that your users will utilize in their app. Call the mount() function when the component is in view/mounts and the unmount() function when the component is unmounted. These functions are described in the Clerk class components.

Use the idiomatic way of your framework for doing this. If you can abstract these repetitions into a re-usable hook/directive, then do that.

import { $clerk } from './stores'

const SignInComponent = (props: SignInProps) => {
  const el = ref()

  function onMount() {
    $clerk.mountSignIn(el, props)
  }

  function onUnMount() {
    $clerk.unmountSignIn(el)
  }
}

</Steps>

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