Node.js compatibility

Most Workers import one or more packages of JavaScript or TypeScript code from npm ↗ as dependencies in package.json. Many of these packages rely on APIs from the Node.js runtime ↗, and will not work unless these APIs are present.

To ensure compatibility with a wider set of npm packages, and make it easier for you to run existing applications on Cloudflare Workers, the following APIs from the Node.js runtime ↗ are available directly as Workers runtime APIs, with no need to add polyfills to your own code:

• assert
• AsyncLocalStorage
• Buffer
• Crypto
• Diagnostics Channel
• EventEmitter
• path
• process
• Streams
• StringDecoder
• test
• util

Node.js APIs are available under the node: prefix, and this prefix must be used when importing modules, both in your code and the npm packages you depend on.

// Do this:
import { Buffer } from "node:buffer";

// Do not do this:
import { Buffer } from "buffer";

Unless otherwise specified, implementations of Node.js APIs in Workers are intended to match the implementation in the Current release of Node.js ↗.

Enable Node.js with Workers

Add the nodejs_compat compatibility flag to your wrangler.toml:

wrangler.toml

compatibility_flags = [ "nodejs_compat" ]

Enable Node.js with Pages Functions

Enable Node.js with Wrangler

To enable nodejs_compat in local development, pass the --compatibility-flags argument with the nodejs_compat flag to wrangler pages dev:

npx wrangler pages dev [<DIRECTORY>] --compatibility-flags="nodejs_compat"

For additional options, refer to the list of Pages-specific CLI commands.

Enable Node.js from the Cloudflare dashboard

To enable Node.js for your Pages Function from the Cloudflare dashboard:

1. Log in to the Cloudflare dashboard ↗ and select your account.
2. Select Workers & Pages and in Overview, select your Pages project.
3. Select Settings > Functions > Compatibility Flags.
4. Add the nodejs_compat compatibility flag to your Preview and Production deployments.

Enable only AsyncLocalStorage

To enable the Node.js AsyncLocalStorage API only, use the nodejs_als compatibility flag.

compatibility_flags = [ "nodejs_als" ]

Related resources

• Write your Worker code in ES modules syntax for an optimized experience.