To deploy to [Cloudflare Workers](https://workers.cloudflare.com/), use [`adapter-cloudflare`](https://github.com/sveltejs/kit/tree/main/packages/adapter-cloudflare). This adapter will be installed by default when you use [`adapter-auto`](adapter-auto). If you plan on staying with Cloudflare, you can switch from [`adapter-auto`](adapter-auto) to using this adapter directly so that `cloudflare:workers` is emulated during local development, type declarations are automatically applied, and the ability to set Cloudflare-specific options is provided. ## Comparisons - `adapter-cloudflare` – supports all SvelteKit features; builds for Cloudflare Workers Static Assets - `adapter-cloudflare-workers` – deprecated. Supports all SvelteKit features; builds for Cloudflare Workers Sites - `adapter-static` – only produces client-side static assets; compatible with Cloudflare Workers Static Assets and Cloudflare Pages ## Usage Run [`npx sv add sveltekit-adapter="adapter:cloudflare"`](/docs/cli/sveltekit-adapter), or install with `npm i -D @sveltejs/adapter-cloudflare` and add the adapter to your `vite.config.js`: ```js // @errors: 2307 /// file: vite.config.js import adapter from '@sveltejs/adapter-cloudflare'; import { sveltekit } from '@sveltejs/kit/vite'; import { defineConfig } from 'vite'; export default defineConfig({ plugins: [ sveltekit({ adapter: adapter({ // See below for an explanation of these options config: undefined, platformProxy: { configPath: undefined, environment: undefined, persist: undefined }, fallback: 'plaintext' }) }) ] }); ``` ## Options ### config Path to your [Wrangler configuration file](https://developers.cloudflare.com/workers/wrangler/configuration/). If you would like to use a Wrangler configuration filename other than `wrangler.jsonc`, `wrangler.json`, or `wrangler.toml` you can specify it using this option. ### platformProxy Preferences for the emulated `env` local bindings. See the [getPlatformProxy](https://developers.cloudflare.com/workers/wrangler/api/#parameters-1) Wrangler API documentation for a full list of options. ### fallback Whether to render a plaintext 404.html page or a rendered SPA fallback page for non-matching asset requests. For Cloudflare Workers, the default behaviour is to return a null-body 404-status response for non-matching assets requests. However, if the [`assets.not_found_handling`](https://developers.cloudflare.com/workers/static-assets/routing/#2-not_found_handling) Wrangler configuration setting is set to `"404-page"`, this page will be served if a request fails to match an asset. If `assets.not_found_handling` is set to `"single-page-application"`, the adapter will render a SPA fallback `index.html` page regardless of the `fallback` option specified. ## Basic configuration The adapter expects to find a [Wrangler configuration file](https://developers.cloudflare.com/workers/wrangler/configuration/) in the project root. It should look something like this: ```jsonc /// file: wrangler.jsonc { "name": "", "main": ".svelte-kit/cloudflare/_worker.js", "compatibility_flags": ["nodejs_als"], "compatibility_date": "", "assets": { "binding": "ASSETS", "directory": ".svelte-kit/cloudflare", } } ``` ## Deployment You can use the Wrangler CLI to deploy your application by running `npx wrangler deploy` or use the [Cloudflare Git integration](https://developers.cloudflare.com/workers/ci-cd/builds/) to enable automatic builds and deployments on push. ## Runtime APIs The [`env`](https://developers.cloudflare.com/workers/runtime-apis/fetch-event#parameters) object contains your project's [bindings](https://developers.cloudflare.com/workers/runtime-apis/bindings/), which consist of KV/DO namespaces, etc. It is available on the [`cloudflare:workers`](https://developers.cloudflare.com/workers/runtime-apis/bindings/#importing-env-as-a-global) module. ```js /// file: +server.js // @filename: ambient.d.ts declare module 'cloudflare:workers' { export const env: { YOUR_DURABLE_OBJECT_NAMESPACE: import('@cloudflare/workers-types').DurableObjectNamespace; }; } // @filename: +server.js // ---cut--- // @errors: 2355 2322 import { env } from 'cloudflare:workers'; /** @type {import('./$types').RequestHandler} */ export async function POST() { const x = env.YOUR_DURABLE_OBJECT_NAMESPACE.idFromName('x'); } ``` > [!NOTE] SvelteKit's built-in [`$app/env/*` modules](environment-variables) should be preferred for environment variables. To make these types available to your app, install [`wrangler`](https://www.npmjs.com/package/wrangler) and run [`wrangler types`](https://developers.cloudflare.com/workers/languages/typescript/). ### Testing locally Cloudflare specific values are emulated during dev and preview modes. Local [bindings](https://developers.cloudflare.com/workers/wrangler/configuration/#bindings) are created based on your [Wrangler configuration file](https://developers.cloudflare.com/workers/wrangler/) and are used to populate `env` during development and preview. Use the adapter config [`platformProxy` option](#Options-platformProxy) to change your preferences for the bindings. > [!NOTE] [Durable Objects](https://developers.cloudflare.com/durable-objects/) and [Workflows](https://developers.cloudflare.com/workflows/), which require custom classes to be exported from your worker, are not currently supported. For testing the build, you should use [Wrangler](https://developers.cloudflare.com/workers/wrangler/) version 4. Once you have built your site, run `wrangler dev`. ## Headers and redirects The [`_headers`](https://developers.cloudflare.com/workers/static-assets/headers/) and [`_redirects`](https://developers.cloudflare.com/workers/static-assets/redirects/) files, specific to Cloudflare, can be used for static asset responses (like images) by putting them into the project root folder. However, they will have no effect on responses dynamically rendered by SvelteKit, which should return custom headers or redirect responses from [server endpoints](routing#server) or with the [`handle`](hooks#handle) hook. ## Troubleshooting ### Node.js compatibility If you would like to enable [Node.js compatibility](https://developers.cloudflare.com/workers/runtime-apis/nodejs/), you can add the `nodejs_compat` compatibility flag to your Wrangler configuration file: ```jsonc /// file: wrangler.jsonc { "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](https://developers.cloudflare.com/workers/platform/limits/#worker-size) 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](./faq#How-do-I-use-a-client-side-library-accessing-document-or-window) for more information. ### Accessing the file system You can't use `fs` in Cloudflare Workers. Instead, use the [`read`]($app-server#read) function from `$app/server` to access your files. It works by fetching the file from the deployed public assets location. Alternatively, you can [prerender](page-options#prerender) the routes in question. ## Migrating from Workers Sites Cloudflare no longer recommends using [Workers Sites](https://developers.cloudflare.com/workers/configuration/sites/configuration/) and instead recommends using [Workers Static Assets](https://developers.cloudflare.com/workers/static-assets/). To migrate, replace `@sveltejs/adapter-cloudflare-workers` with `@sveltejs/adapter-cloudflare` and remove all `site` configuration settings from your Wrangler configuration file, then add the `assets.directory` and `assets.binding` configuration settings: ```js // @errors: 2307 /// file: vite.config.js +++import adapter from '@sveltejs/adapter-cloudflare';+++ import { sveltekit } from '@sveltejs/kit/vite'; import { defineConfig } from 'vite'; export default defineConfig({ plugins: [ sveltekit({ +++adapter: adapter()+++ }) ] }); ``` ### wrangler.toml ```toml /// file: wrangler.toml ---site.bucket = ".cloudflare/public"--- +++assets.directory = ".cloudflare/public" assets.binding = "ASSETS" # Exclude this if you don't have a `main` key configured.+++ ``` ### wrangler.jsonc ```jsonc /// file: wrangler.jsonc { --- "site": { "bucket": ".cloudflare/public" },--- +++ "assets": { "directory": ".cloudflare/public", "binding": "ASSETS" // Exclude this if you don't have a `main` key configured. }+++ } ``` ## Migrating from Cloudflare Pages To migrate to Cloudflare Workers: 1. Remove `pages_build_output_dir` from your Wrangler configuration and [add the `main` and `assets` settings](#Basic-configuration). 2. Remove the adapter's `routes` option and any `_routes.json` files. 3. Replace `wrangler pages dev` and `wrangler pages deploy` with `wrangler dev` and `wrangler deploy`. For automatic deployments, use [Workers Builds](https://developers.cloudflare.com/workers/ci-cd/builds/) instead of the Pages Git integration. See Cloudflare's [Workers and Pages compatibility matrix](https://developers.cloudflare.com/workers/static-assets/migration-guides/migrate-from-pages/#compatibility-matrix) for a comparison of supported features.