facebook/react · error

The React Server cannot be used outside a react-server envir

Error message

The React Server cannot be used outside a react-server environment. You must configure Node.js using the `--conditions react-server` flag.

What it means

The source-level server entry of react-server-dom-esm: importing the server module outside a react-server environment throws at module load. The server writer only resolves under the 'react-server' export condition; in any other condition the module graph intentionally fails fast with instructions to configure Node with --conditions react-server. This keeps server-only code from ever executing in a client bundle or plain Node process.

Source

Thrown at packages/react-server-dom-esm/server.js:10

/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow
 */

throw new Error(
  'The React Server cannot be used outside a react-server environment. ' +
    'You must configure Node.js using the `--conditions react-server` flag.',
);

View on GitHub (pinned to eafeac097b)

Solutions

1. Start the server with node --conditions react-server
2. Add 'react-server' to resolve conditions for the server build, and ensure the client build never imports the server entry
3. For Jest, set NODE_OPTIONS='--conditions react-server' for server-side test projects
4. Split shared code so the server entry is only reachable from server-only modules

Example fix

// before
// package.json
"scripts": { "start": "node server.js" }

// after
"scripts": { "start": "node --conditions react-server server.js" }

const hasReactServerCondition =
  process.execArgv.some(a => a.includes('react-server'));
if (!hasReactServerCondition) {
  console.error('Run with: node --conditions react-server');
  process.exit(1);
}

When it happens

Trigger: importing 'react-server-dom-esm/server' (renderToPipeableStream and friends) in plain Node without the react-server condition; a client bundle graph that transitively reaches the server entry; tooling (bundler, test runner) resolving without custom conditions so the throwing module is selected.

Common situations: RSC servers started without the documented flag; shared modules imported by both client and server where the server import leaks into the client graph; CI running server code through runners that reset NODE_OPTIONS.

Related errors

• The React Server Writer cannot be used outside a react-serve
• The React Server cannot be used outside a react-server envir
• The React Server Writer cannot be used outside a react-serve
• The React Server cannot be used outside a react-server envir
• The React Server Writer cannot be used outside a react-serve

AI-assisted analysis of facebook/react@eafeac097b (2026-08-21). Data as JSON: /api/errors/178bfa8a4ca0b6d7. Report an issue: GitHub.