If you have more than one copy of React DevTools installed and enabled (e.g. the version in the Chrome store and a locally built version) they can interfere with each other.

DevTools should detect this case and warn by showing a dialog in the DevTools UI and/or by logging to the console.

Note that we _should not warn_ if a related tool like Fast Refresh is present, only another copy of DevTools.
/**
 * Copyright (c) Facebook, Inc. and its affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @flow strict-local
 */
declare var chrome: any;
export const CURRENT_EXTENSION_ID = chrome.runtime.id;
export const EXTENSION_INSTALL_CHECK_MESSAGE = 'extension-install-check';
export const CHROME_WEBSTORE_EXTENSION_ID = 'fmkadmapgofadopljbjfkapdkoienihi';
export const INTERNAL_EXTENSION_ID = 'dnjnjgbfilfphmojnmhliehogmojhclc';
export const LOCAL_EXTENSION_ID = 'ikiahnapldjmdmpkmfhjdjilojjhgcbf';
export const EXTENSION_INSTALLATION_TYPE:
  | 'public'
  | 'internal'
  | 'local'
  | 'unknown' =
  CURRENT_EXTENSION_ID === CHROME_WEBSTORE_EXTENSION_ID
    ? 'public'
    : CURRENT_EXTENSION_ID === INTERNAL_EXTENSION_ID
    ? 'internal'
    : CURRENT_EXTENSION_ID === LOCAL_EXTENSION_ID
    ? 'local'
    : 'unknown';