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React render tracker

React render tracker – a tool to discover performance issues related to unintended re-renders

STATUS: MVP / proof of concept

The project is at an early stage of development. Lots of things have yet to be added and polished (see roadmap). Feel free to create an issue if you found a bug or have an idea.



  • Cumulative state of component's tree including unmounted components (can be hidden by a toggle in the top right corner) and number of updates (re-renders)
  • Two types of hierarchy in component's tree: owner-based (created by, better for render tracking, that's by default) and parent-based (composed by)
  • Event log for a component or its subtree, grouped by a React's commit of batch of rendering work, with some details on changes in components like context, state and props
  • Self and total (including subtree rendering) cumulative time or all component renders (hidden by default, use toggle in the right top corner to enable it)
  • Overall stats on events and component instances in status bar
  • More to come... (see roadmap)

How to use

Option 1 – Using with browser's devtools

  1. Add to your html file a script before a React app:
<script src="path/to/react-render-tracker.js"></script>

NOTE: A path for a bundle in the npm package is dist/react-render-tracker.js

You can use CDN services to include script with no installation:

<!-- unpkg -->
<script src=""></script>
<!-- jsdelivr -->
<script src=""></script>
  1. Install Rempl extension for Chromium based browser (other browsers might be added later)

  2. Open your html page and browser's devtools, open Rempl tab. That's it.

Option 2 – Using with a web-socket server

Since project is based on Rempl, it's also possible to use other hosts, e.g. rempl-cli to launch a server. In this case, it is possible to inspect a react application launched in any web view with web sockets support.

  1. Run following commands:
> npm install -g rempl-cli
> rempl

This will launch a Rempl server on port 8177. Use --port option to specify any other port. See more option with rempl --help command.

  1. Add to your html file a script before a React app:
<script src="path/to/react-render-tracker.js"></script>
  1. Add <meta> tag with specified origin of the Rempl server:
<meta name="rempl:server" content="localhost:8177" />
  1. Open your html and url of Rempl server. You should see connected instance of React render tracker, click on it to see UI.

How to start playground locally

npm install
npm start

Open a URL displayed in console (e.g. Server listen on http://localhost:3000).