facebook/react · error · 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

This file is the fallback target of the package's './static' export. The exports map only selects the real static renderer when Node resolves with the react-server condition; without it you get this module, which throws immediately so a server entry never runs in a plain Node process. It enforces that server-side Flight code executes under --conditions react-server.

Source

Thrown at packages/react-server-dom-esm/static.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 Node with --conditions react-server (node --conditions react-server server.mjs) or set it via NODE_OPTIONS
2. Import the explicit variant entry such as 'react-server-dom-esm/static.node', which bypasses the condition gate
3. For bundlers: include react-server in conditionNames only for the server build and never for the client build

Example fix

// before
node server.mjs // imports 'react-server-dom-esm/static' -> throws

// after
node --conditions react-server server.mjs

// run before importing any server entry
const flags = process.execArgv.concat((process.env.NODE_OPTIONS || '').split(' '));
const hasReactServer = flags.some(a => a.includes('react-server'));
if (!hasReactServer) {
  throw new Error('Start with --conditions react-server before loading react-server-dom-esm/server');
}

try {
  const staticRenderer = await import('react-server-dom-esm/static');
} catch (e) {
  if (/react-server environment/.test(e.message)) {
    throw new Error('Restart the process with --conditions react-server');
  }
  throw e;
}

When it happens

Trigger: Importing 'react-server-dom-esm/static' or './server' in a Node process started without --conditions react-server; a bundler resolving the exports map without react-server in conditionNames; deep-importing the static.js file directly instead of through the exports map.

Common situations: Forgetting the flag in dev scripts, tests, or process-manager configs; bundlers (webpack/vite) resolving the server entry into a browser build; version upgrades where the exports map gained the condition gates.

Related errors

• The React Server Writer cannot be used outside a react-serve
• 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 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/1aa91a37817557b6. Report an issue: GitHub.