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' })
	}
};

If you would like to enable Node.js compatibility, you can add "nodejs_compat" flag to wrangler.toml:

compatibility_flags = [ "nodejs_compat" ]

Runtime APIspermalink

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, caches, and cf, 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 include type declarations for your bindings, 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

Cloudflare Workers specific values in the platform property are emulated during dev and preview modes. The bindings in your wrangler.toml will be used to populate platform.env during local development.

For testing the build, you should use wrangler version 3. Once you have built your site, run wrangler dev.

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 use fs in Cloudflare Workers — you must prerender the routes in question.