Cloudflare Workers

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

Comparisons

• adapter-cloudflare-workers – supports all SvelteKit features; builds for Cloudflare Workers
• adapter-cloudflare – supports all SvelteKit features; builds for Cloudflare Pages
• adapter-static – only produces client-side static assets; compatible with Cloudflare Pages and Cloudflare Workers

Usage

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

import import adapteradapter from '@sveltejs/adapter-cloudflare-workers';

export default {
	
kit: {
    adapter: any;
}kit: {
		adapter: anyadapter: import adapteradapter({
			// see below for options that can be set here
		})
	}
};

Options

config

Path to your Wrangler configuration file. If you would like to use a Wrangler configuration filename other than wrangler.jsonc, you can specify it using this option.

platformProxy

Preferences for the emulated platform.env local bindings. See the getPlatformProxy Wrangler API documentation for a full list of options.

Basic configuration

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

{
	"name": "<your-service-name>",
	"main": ".svelte-kit/cloudflare/_worker.js",
	"compatibility_date": "2025-01-01",
	"assets": {
		"binding": "ASSETS",
		"directory": ".svelte-kit/cloudflare",
	}
}

Deployment

Please follow the framework guide for Cloudflare Workers to begin.

Runtime APIs

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:

export async function 
function POST({ request, platform }: {
    request: any;
    platform: any;
}): Promise<void>POST({ request, platform }) {

	const const x: anyx = platform: anyplatform.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, install @cloudflare/workers-types and reference them in your src/app.d.ts:

import { interface KVNamespace<Key extends string = string>KVNamespace, interface DurableObjectNamespace<T extends Rpc.DurableObjectBranded | undefined = undefined>DurableObjectNamespace } from '@cloudflare/workers-types';

declare global {
	namespace App {
		interface interface App.Platform
If your adapter provides platform-specific context via event.platform, you can specify it here.
Platform {
			
App.Platform.env?: {
    YOUR_KV_NAMESPACE: KVNamespace;
    YOUR_DURABLE_OBJECT_NAMESPACE: DurableObjectNamespace;
} | undefinedenv?: {
				type YOUR_KV_NAMESPACE: KVNamespace<string>YOUR_KV_NAMESPACE: interface KVNamespace<Key extends string = string>KVNamespace;
				type YOUR_DURABLE_OBJECT_NAMESPACE: DurableObjectNamespace<undefined>YOUR_DURABLE_OBJECT_NAMESPACE: interface DurableObjectNamespace<T extends Rpc.DurableObjectBranded | undefined = undefined>DurableObjectNamespace;
			};
		}
	}
}

export {};

Testing locally

Cloudflare Workers specific values in the platform property are emulated during dev and preview modes. Local bindings are created based on your Wrangler configuration file and are used to populate platform.env during development and preview. Use the adapter config platformProxy option to change your preferences for the bindings.

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

Notes

The _headers and _redirects files specific to Cloudflare Pages can be used for static asset responses (like images) by putting them into the project root folder.

Troubleshooting

Node.js compatibility

If you would like to enable Node.js compatibility, you can add the nodejs_compat compatibility flag to your Wrangler configuration file:

{
	"compatibility_flags": ["nodejs_compat"]
}

Worker size limits

When deploying your application, 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 system

You can’t use fs in Cloudflare Workers — you must prerender the routes in question.

Migrating from Workers Sites to Workers Static Assets

Cloudflare no longer recommends using Workers Sites and instead recommends using Workers Static Assets. To migrate, remove all site configuration settings from your Wrangler configuration file and add the assets.directory and assets.binding configuration settings:

wrangler.toml

site.bucket = ".cloudflare/public"
assets.directory = ".cloudflare/public"
assets.binding = "ASSETS"

wrangler.jsonc

{
	"site": {
		"bucket": ".cloudflare/public"
	},
	"assets": {
		"directory": ".cloudflare/public",
		"binding": "ASSETS"
	}
}