Cloudflare Workers

To deploy to Cloudflare Workers, use adapter-cloudflare-workers.

Unless you have a specific reason to use adapter-cloudflare-workers, it's recommended that you use adapter-cloudflare instead. Both adapters have equivalent functionality, but Cloudflare Pages offers features like GitHub integration with automatic builds and deploys, preview deployments, instant rollback and so on.

Usagepermalink

Install with npm i -D @sveltejs/adapter-cloudflare-workers, then add the adapter to your svelte.config.js:

ts
import adapter from '@sveltejs/adapter-cloudflare-workers';
Cannot find module '@sveltejs/adapter-cloudflare-workers' or its corresponding type declarations.2307Cannot find module '@sveltejs/adapter-cloudflare-workers' or its corresponding type declarations.
 
export default {
  kit: {
    adapter: adapter()
  }
};

Basic Configurationpermalink

This adapter expects to find a wrangler.toml file in the project root. It should look something like this:

name = "<your-service-name>"
account_id = "<your-account-id>"

main = "./.cloudflare/worker.js"
site.bucket = "./.cloudflare/public"

build.command = "npm run build"

compatibility_date = "2021-11-12"
workers_dev = true

<your-service-name> can be anything. <your-account-id> can be found by logging into your Cloudflare dashboard and grabbing it from the end of the URL:

https://dash.cloudflare.com/<your-account-id>

You should add the .cloudflare directory (or whichever directories you specified for main and site.bucket) to your .gitignore.

You will need to install wrangler and log in, if you haven't already:

npm i -g wrangler
wrangler login

Then, you can build your app and deploy it:

wrangler deploy

Custom configpermalink

If you would like to use a config file other than wrangler.toml, you can do like so:

ts
import adapter from '@sveltejs/adapter-cloudflare-workers';
Cannot find module '@sveltejs/adapter-cloudflare-workers' or its corresponding type declarations.2307Cannot find module '@sveltejs/adapter-cloudflare-workers' or its corresponding type declarations.
 
export default {
  kit: {
    adapter: adapter({ config: '<your-wrangler-name>.toml' })
  }
};

Bindingspermalink

The env object contains your project's bindings, which consist of KV/DO namespaces, etc. It is passed to SvelteKit via the platform property, along with context and caches, meaning that you can access it in hooks and endpoints:

ts
export async function POST({ request, platform }) {
Binding element 'request' implicitly has an 'any' type.
Binding element 'platform' implicitly has an 'any' type.7031
7031Binding element 'request' implicitly has an 'any' type.
Binding element 'platform' implicitly has an 'any' type.
  const x = platform.env.YOUR_DURABLE_OBJECT_NAMESPACE.idFromName('x');
}

SvelteKit's built-in $env module should be preferred for environment variables.

To make these types available to your app, reference them in your src/app.d.ts:

declare global {
  namespace App {
    interface Platform {
			env?: {
				YOUR_KV_NAMESPACE: KVNamespace;
				YOUR_DURABLE_OBJECT_NAMESPACE: DurableObjectNamespace;
			};
    }
  }
}

export {};

Testing Locallypermalink

platform.env is only available in the final build and not in dev mode. For testing the build, you can use wrangler. Once you have built your site, run wrangler dev. Ensure you have your bindings in your wrangler.toml. Wrangler version 3 is recommended.

Troubleshootingpermalink

Worker size limitspermalink

When deploying to workers, the server generated by SvelteKit is bundled into a single file. Wrangler will fail to publish your worker if it exceeds the size limits after minification. You're unlikely to hit this limit usually, but some large libraries can cause this to happen. In that case, you can try to reduce the size of your worker by only importing such libraries on the client side. See the FAQ for more information.

Accessing the file systempermalink

You can't access the file system through methods like fs.readFileSync in Serverless/Edge environments. If you need to access files that way, do that during building the app through prerendering. If you have a blog for example and don't want to manage your content through a CMS, then you need to prerender the content (or prerender the endpoint from which you get it) and redeploy your blog everytime you add new content.