# captcha prop The `captcha` property can be used to change the appearance of the CAPTCHA widget. ## Properties | Name | Type | Description | | ----------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------- | | theme | 'auto' | 'light' | 'dark' | The CAPTCHA widget theme. Defaults to auto. | | size | 'normal' | 'flexible' | 'compact' | The CAPTCHA widget size. Defaults to normal. | | appearance.captcha.language: Set by this language property. | localization.locale: Set by the localization prop on . Some languages are supported by Clerk but not by Cloudflare Turnstile, which is used for the CAPTCHA widget. See Cloudflare Turnstile's supported languages. | | ## Usage To customize the CAPTCHA widget, pass the `appearance` prop to the [clerk.load()](https://clerk.com/docs/js-frontend/reference/objects/clerk.md#load) method. The `appearance` prop accepts the property `captcha`, which can be used to apply different changes to the widget. In the following example, the CAPTCHA is customized to use the dark theme, a flexible size, and Spanish as the display language. Use the following tabs to view the code necessary for each file. **main.js** ```js import { Clerk } from '@clerk/clerk-js' const clerkPubKey = import.meta.env.VITE_CLERK_PUBLISHABLE_KEY const clerk = new Clerk(clerkPubKey) await clerk.load({ appearance: { captcha: { theme: 'dark', size: 'flexible', language: 'es-ES', }, }, }) if (clerk.isSignedIn) { document.getElementById('app').innerHTML = `
` const userButtonDiv = document.getElementById('user-button') clerk.mountUserButton(userButtonDiv) } else { document.getElementById('app').innerHTML = `
` const signInDiv = document.getElementById('sign-in') clerk.mountSignIn(signInDiv) } ``` **index.html** ```html Clerk + JavaScript App
``` --- ## Sitemap [Overview of all docs pages](https://clerk.com/docs/llms.txt)