diff --git a/packages/react-devtools-core/README.md b/packages/react-devtools-core/README.md
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+# `react-devtools-core`
+
+A standalone React DevTools implementation.
+
+This is a low-level package. If you're looking for the Electron app you can run, **use `react-devtools` package instead.**
+
+## API
+
+### `react-devtools-core`
+
+This is similar requiring the `react-devtools` package, but provides several configurable options. Unlike `react-devtools`, requiring `react-devtools-core` doesn't connect immediately but instead exports a function:
+
+```js
+const { connectToDevTools } = require("react-devtools-core");
+connectToDevTools({
+  // Config options
+});
+
+```
+
+Run `connectToDevTools()` in the same context as React to set up a connection to DevTools.  
+Be sure to run this function *before* importing e.g. `react`, `react-dom`, `react-native`.
+
+The `options` object may contain:
+* `host: string` (defaults to "localhost") - Websocket will connect to this host.
+* `port: number` (defaults to `8097`) - Websocket will connect to this port.
+* `websocket: Websocket` - Custom websocked to use. Overrides `host` and `port` settings if provided.
+* `resolveNativeStyle: (style: number) => ?Object` - Used by the React Native style plug-in.
+* `isAppActive: () => boolean` - If provided, DevTools will poll this method and wait until it returns true before connecting to React.
+
+## `react-devtools-core/standalone`
+
+Renders the DevTools interface into a DOM node.
+
+```js
+require("react-devtools-core/standalone")
+  .setContentDOMNode(document.getElementById("container"))
+  .setStatusListener(status => {
+    // This callback is optional...
+  })
+  .startServer(port);
+```
+
+Reference the `react-devtools` package for a complete integration example.
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diff --git a/packages/react-devtools-inline/README.md b/packages/react-devtools-inline/README.md
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+# `react-devtools-inline`
+
+React DevTools implementation for embedding within a browser-based IDE (e.g. [CodeSandbox](https://codesandbox.io/), [StackBlitz](https://stackblitz.com/)).
+
+This is a low-level package. If you're looking for the standalone DevTools app, **use the `react-devtools` package instead.**
+
+## Usage
+
+This package exports two entry points: a frontend (to be run in the main `window`) and a backend (to be installed and run within an `iframe`<sup>1</sup>).
+
+The frontend and backend can be initialized in any order, but **the backend must not be activated until after the frontend has been initialized**. Because of this, the simplest sequence is:
+
+1. Frontend (DevTools interface) initialized in the main `window`.
+1. Backend initialized in an `iframe`.
+1. Backend activated.
+
+<sup>1</sup> Sandboxed iframes are supported.
+
+## API
+
+### `react-devtools-inline/backend`
+
+* **`initialize(contentWindow)`** -
+Installs the global hook on the window. This hook is how React and DevTools communicate. **This method must be called before React is loaded.** (This means before any `import` or `require` statements!)
+* **`activate(contentWindow)`** -
+Lets the backend know when the frontend is ready. It should not be called until after the frontend has been initialized, else the frontend might miss important tree-initialization events.
+
+```js
+import { activate, initialize } from 'react-devtools-inline/backend';
+
+// Call this before importing React (or any other packages that might import React).
+initialize();
+
+// Call this only once the frontend has been initialized.
+activate();
+```
+
+### `react-devtools-inline/frontend`
+
+* **`initialize(contentWindow)`** -
+Configures the DevTools interface to listen to the `window` the backend was injected into. This method returns a React component that can be rendered directly<sup>2</sup>.
+
+```js
+import { initialize } from 'react-devtools-inline/frontend';
+
+// This should be the iframe the backend hook has been installed in.
+const iframe = document.getElementById(frameID);
+const contentWindow = iframe.contentWindow;
+
+// This returns a React component that can be rendered into your app.
+// <DevTools {...props} />
+const DevTools = initialize(contentWindow);
+```
+
+<sup>2</sup> Because the DevTools interface makes use of several new React APIs (e.g. suspense, concurrent mode) it should be rendered using either `ReactDOM.unstable_createRoot` or `ReactDOM.unstable_createSyncRoot`. It should not be rendered with `ReactDOM.render`.
+
+## Examples
+
+### Configuring a same-origin `iframe`
+
+The simplest way to use this package is to install the hook from the parent `window`. This is possible if the `iframe` is not sandboxed and there are no cross-origin restrictions.
+
+```js
+import {
+  activate as activateBackend,
+  initialize as initializeBackend
+} from 'react-devtools-inline/backend';
+import { initialize as initializeFrontend } from 'react-devtools-inline/frontend';
+
+// The React app you want to inspect with DevTools is running within this iframe:
+const iframe = document.getElementById('target');
+const { contentWindow } = iframe;
+
+// Installs the global hook into the iframe.
+// This must be called before React is loaded into that frame.
+initializeBackend(contentWindow);
+
+// React application can be injected into <iframe> at any time now...
+// Note that this would need to be done via <script> tag injection,
+// as setting the src of the <iframe> would load a new page (withou the injected backend).
+
+// Initialize DevTools UI to listen to the hook we just installed.
+// This returns a React component we can render anywhere in the parent window.
+const DevTools = initializeFrontend(contentWindow);
+
+// <DevTools /> interface can be rendered in the parent window at any time now...
+// Be sure to use either ReactDOM.unstable_createRoot()
+// or ReactDOM.unstable_createSyncRoot() to render this component.
+
+// Let the backend know the frontend is ready and listening.
+activateBackend(contentWindow);
+```
+
+### Configuring a sandboxed `iframe`
+
+Sandboxed `iframe`s are also supported but require more complex initialization.
+
+**`iframe.html`**
+```js
+import { activate, initialize } from "react-devtools-inline/backend";
+
+// The DevTooks hook needs to be installed before React is even required!
+// The safest way to do this is probably to install it in a separate script tag.
+initialize(window);
+
+// Wait for the frontend to let us know that it's ready.
+function onMessage({ data }) {
+  switch (data.type) {
+    case "activate-backend":
+      window.removeEventListener("message", onMessage);
+
+      activate(window);
+      break;
+    default:
+      break;
+  }
+}
+
+window.addEventListener("message", onMessage);
+```
+
+**`main-window.html`**
+```js
+import { initialize } from "react-devtools-inline/frontend";
+
+const iframe = document.getElementById("target");
+const { contentWindow } = iframe;
+
+// Initialize DevTools UI to listen to the iframe.
+// This returns a React component we can render anywhere in the main window.
+// Be sure to use either ReactDOM.unstable_createRoot()
+// or ReactDOM.unstable_createSyncRoot() to render this component.
+const DevTools = initialize(contentWindow);
+
+// Let the backend know to initialize itself.
+// We can't do this directly because the iframe is sandboxed.
+// Only initialize the backend once the DevTools frontend has been initialized.
+iframe.onload = () => {
+  contentWindow.postMessage(
+    {
+      type: "activate-backend"
+    },
+    "*"
+  );
+};
+```
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diff --git a/packages/react-devtools/CHANGELOG.md b/packages/react-devtools/CHANGELOG.md
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+# React DevTools changelog
+
+<!-- ## [Unreleased]
+<details>
+  <summary>
+    Changes that have landed in master but are not yet released.
+    Click to see more.
+  </summary>
+  
+  <!-- Upcoming changes go here
+</details> -->
+
+## 4.0.0 (release date TBD)
+
+### General changes
+
+#### Improved performance
+The legacy DevTools extension used to add significant performance overhead, making it unusable for some larger React applications. That overhead has been effectively eliminated in version 4.
+
+[Learn more](https://github.com/bvaughn/react-devtools-experimental/blob/master/OVERVIEW.md) about the performance optimizations that made this possible.
+
+#### Component stacks
+
+React component authors have often requested a way to log warnings that include the React ["component stack"](https://reactjs.org/docs/error-boundaries.html#component-stack-traces). DevTools now provides an option to automatically append this information to warnings (`console.warn`) and errors (`console.error`).
+
+![Example console warning with component stack added](https://user-images.githubusercontent.com/29597/62228120-eec3da80-b371-11e9-81bb-018c1e577389.png)
+
+It can be disabled in the general settings panel:
+
+![Settings panel showing "component stacks" option](https://user-images.githubusercontent.com/29597/62227882-8f65ca80-b371-11e9-8a4e-5d27011ad1aa.png)
+
+### Components tree changes
+
+#### Component filters
+
+Large component trees can sometimes be hard to navigate. DevTools now provides a way to filter components so that you can hide ones you're not interested in seeing.
+
+![Component filter demo video](https://user-images.githubusercontent.com/29597/62229209-0bf9a880-b374-11e9-8f84-cebd6c1a016b.gif)
+
+Host nodes (e.g. HTML `<div>`, React Native `View`) are now hidden by default, but you can see them by disabling that filter.
+
+Filter preferences are remembered between sessions.
+
+#### No more in-line props
+
+Components in the tree no longer show in-line props. This was done to [make DevTools faster](https://github.com/bvaughn/react-devtools-experimental/blob/master/OVERVIEW.md) and to make it easier to browse larger component trees.
+
+You can view a component's props, state, and hooks by selecting it:
+
+![Inspecting props](https://user-images.githubusercontent.com/29597/62303001-37da6400-b430-11e9-87fd-10a94df88efa.png)
+
+#### "Rendered by" list
+
+In React, an element's "owner" refers the thing that rendered it. Sometimes an element's parent is also its owner, but usually they're different. This distinction is important because props come from owners.
+
+![Example code](https://user-images.githubusercontent.com/29597/62229551-bbcf1600-b374-11e9-8411-8ff411f4f847.png)
+
+When you are debugging an unexpected prop value, you can save time if you skip over the parents.
+
+DevTools v4 adds a new "rendered by" list in the right hand pane that allows you to quickly step through the list of owners to speed up your debugging.
+
+![Example video showing the "rendered by" list](https://user-images.githubusercontent.com/29597/62229747-4152c600-b375-11e9-9930-3f6b3b92be7a.gif)
+
+#### Owners tree
+
+The inverse of the "rendered by" list is called the "owners tree". It is the list of things rendered by a particular component- (the things it "owns"). This view is kind of like looking at the source of the component's render method, and can be a helpful way to explore large, unfamiliar React applications.
+
+Double click a component to view the owners tree and click the "x" button to return to the full component tree:
+
+![Demo showing "owners tree" feature](https://user-images.githubusercontent.com/29597/62229452-84f90000-b374-11e9-818a-61eec6be0bb4.gif)
+
+#### No more horizontal scrolling
+
+Deeply nested components used to require both vertical and horizontal scrolling to see, making it easy to "get lost" within large component trees. DevTools now dynamically adjusts nesting indentation to eliminate horizontal scrolling.
+
+![Video demonstration dynamic indentation to eliminate horizontal scrolling](https://user-images.githubusercontent.com/29597/62246661-f8ad0400-b398-11e9-885f-284f150a6d76.gif)
+
+#### Improved hooks support
+
+Hooks now have the same level of support as props and state: values can be edited, arrays and objects can be drilled into, etc.
+
+![Video demonstrating hooks support](https://user-images.githubusercontent.com/29597/62230532-d86c4d80-b376-11e9-8629-1b2129b210d6.gif)
+
+#### Improved search UX
+
+Legacy DevTools search filtered the components tree to show matching nodes as roots. This made the overall structure of the application harder to reason about, because it displayed ancestors as siblings.
+
+Search results are now shown inline similar to the browser's find-in-page search.
+
+![Video demonstrating the search UX](https://user-images.githubusercontent.com/29597/62230923-c63edf00-b377-11e9-9f95-aa62ddc8f62c.gif)
+
+#### Higher order components
+
+[Higher order components](https://reactjs.org/docs/higher-order-components.html) (or HOCs) often provide a [custom `displayName`](https://reactjs.org/docs/higher-order-components.html#convention-wrap-the-display-name-for-easy-debugging) following a convention of `withHOC(InnerComponentName)` in order to make it easier to identify components in React warnings and in DevTools.
+
+The new Components tree formats these HOC names (along with several built-in utilities like `React.memo` and `React.forwardRef`) as a special badge to the right of the decorated component name.
+
+![Screenshot showing HOC badges](https://user-images.githubusercontent.com/29597/62302774-c4385700-b42f-11e9-9ef4-49c5f18d6276.png)
+
+Components decorated with multiple HOCs show the topmost badge and a count. Selecting the component shows all of the HOCs badges in the properties panel.
+
+![Screenshot showing a component with multiple HOC badges](https://user-images.githubusercontent.com/29597/62303729-7fadbb00-b431-11e9-8685-45f5ab52b30b.png)
+
+#### Suspense toggle
+
+React's experimental [Suspense API](https://reactjs.org/docs/react-api.html#suspense) lets components "wait" for something before rendering. `<Suspense>` components can be used to specify loading states when components deeper in the tree are waiting to render.
+
+DevTools lets you test these loading states with a new toggle:
+
+![Video demonstrating suspense toggle UI](https://user-images.githubusercontent.com/29597/62231446-e15e1e80-b378-11e9-92d4-086751dc65fc.gif)
+
+### Profiler changes
+
+#### Reload and profile
+
+The profiler is a powerful tool for performance tuning React components. Legacy DevTools supported profiling, but only after it detected a profiling-capable version of React. Because of this there was no way to profile the initial _mount_ (one of the most performance sensitive parts) of an application.
+
+This feature is now supported with a "reload and profile" action:
+
+![Video demonstrating the reload-and-profile feature](https://user-images.githubusercontent.com/29597/62233455-7a8f3400-b37d-11e9-9563-ec334bfb2572.gif)
+
+#### Import/export
+
+Profiler data can now be exported and shared with other developers to enable easier collaboration.
+
+![Video demonstrating exporting and importing profiler data](https://user-images.githubusercontent.com/29597/62233911-6566d500-b37e-11e9-9052-692378c92538.gif)
+
+Exports include all commits, timings, interactions, etc.
+
+#### "Why did this render?"
+
+"Why did this render?" is a common question when profiling. The profiler now helps answer this question by recording which props and state change between renders.
+
+![Video demonstrating profiler "why did this render?" feature](https://user-images.githubusercontent.com/29597/62234698-0f932c80-b380-11e9-8cf3-a5183af0c388.gif)
+
+Because this feature adds a small amount of overhead, it can be disabled in the profiler settings panel.
+
+#### Component renders list
+
+The profiler now displays a list of each time the selected component rendered during a profiling session, along with the duration of each render. This list can be used to quickly jump between commits when analyzing the performance of a specific component.
+
+![Video demonstrating profiler's component renders list](https://user-images.githubusercontent.com/29597/62234547-bcb97500-b37f-11e9-9615-54fba8b574b9.gif)
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diff --git a/packages/react-devtools/README.md b/packages/react-devtools/README.md
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+# `react-devtools`
+
+React DevTools is available as a built-in extension for Chrome and Firefox browsers. This package enables you to debug a React app elsewhere (e.g. a mobile browser, an embedded webview, Safari, inside an iframe).
+
+It works both with React DOM and React Native.
+
+<img src="http://i.imgur.com/IXeHiZD.png" width="600" alt="Screenshot of React DevTools running with React Native">
+
+## Installation
+Install the `react-devtools` package. Because this is a development tool, a global install is often the most convenient:
+```sh
+# Yarn
+yarn global add react-devtools
+
+# NPM
+npm install -g react-devtools
+```
+
+If you prefer to avoid global installations, you can add `react-devtools` as a project dependency. With Yarn, you can do this by running:
+```sh
+yarn add --dev react-devtools
+```
+
+With NPM you can just use [NPX](https://www.npmjs.com/package/npx):
+```sh
+npx react-devtools
+```
+
+## Usage with React Native
+Run `react-devtools` from the terminal to launch the standalone DevTools app:
+```sh
+react-devtools
+```
+
+If you're not in a simulator then you also need to run the following in a command prompt:
+```sh
+adb reverse tcp:8097 tcp:8097
+```
+
+If you're using React Native 0.43 or higher, it should connect to your simulator within a few seconds.
+
+### Integration with React Native Inspector
+
+You can open the [in-app developer menu](https://facebook.github.io/react-native/docs/debugging.html#accessing-the-in-app-developer-menu) and choose "Show Inspector". It will bring up an overlay that lets you tap on any UI element and see information about it:
+
+![React Native Inspector](http://i.imgur.com/ReFhREb.gif)
+
+However, when `react-devtools` is running, Inspector will enter a special collapsed mode, and instead use the DevTools as primary UI. In this mode, clicking on something in the simulator will bring up the relevant components in the DevTools:
+
+![React DevTools Inspector Integration](http://i.imgur.com/wVgV9RP.gif)
+
+You can choose "Hide Inspector" in the same menu to exit this mode.
+
+### Inspecting Component Instances
+
+When debugging JavaScript in Chrome, you can inspect the props and state of the React components in the browser console.
+
+First, follow the [instructions for debugging in Chrome](https://facebook.github.io/react-native/docs/debugging.html#chrome-developer-tools) to open the Chrome console.
+
+Make sure that the dropdown in the top left corner of the Chrome console says `debuggerWorker.js`. **This step is essential.**
+
+Then select a React component in React DevTools. There is a search box at the top that helps you find one by name. As soon as you select it, it will be available as `$r` in the Chrome console, letting you inspect its props, state, and instance properties.
+
+![React DevTools Chrome Console Integration](http://i.imgur.com/Cpvhs8i.gif)
+
+
+## Usage with React DOM
+
+The standalone shell can also be useful with React DOM (e.g. to debug apps in Safari or inside of an iframe).
+
+Run `react-devtools` from the terminal to launch the standalone DevTools app:
+```sh
+react-devtools
+```
+
+Add `<script src="http://localhost:8097"></script>` as the very first `<script>` tag in the `<head>` of your page when developing:
+
+```html
+<!doctype html>
+<html lang="en">
+  <head>
+    <script src="http://localhost:8097"></script>
+```
+
+This will ensure the developer tools are connected. **Don’t forget to remove it before deploying to production!**
+
+>If you install `react-devtools` as a project dependency, you may also replace the `<script>` suggested above with a JavaScript import (`import 'react-devtools'`). It is important that this import comes before any other imports in your app (especially before `react-dom`). Make sure to remove the import before deploying to production, as it carries a large DevTools client with it. If you use Webpack and have control over its configuration, you could alternatively add `'react-devtools'` as the first item in the `entry` array of the development-only configuration, and then you wouldn’t need to deal either with `<script>` tags or `import` statements.
+
+## Advanced
+
+By default DevTools listen to port `8097` on `localhost`. If you need to customize host, port, or other settings, see the `react-devtools-core` package instead.
+
+## Developing
+
+* Run `yarn start:backend` and `yarn start:standalone` in `../react-devtools-core`
+* Run `yarn start` in this folder
+* Refresh the app after it has recompiled a change
+* For React Native, copy `react-devtools-core` to its `node_modules` to test your changes.
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