Awesome Open Source
Awesome Open Source

⚑ React Performance πŸš€ EpicReact.Dev

React is fast, until it isn't

Learn everything you need to diagnose, profile, and fix performance problems in your React application using the Browser Performance Profiler, React DevTools Profiler, and proven React optimization techniques.

Learn React from Start to Finish

Build Status All Contributors GPL 3.0 License Code of Conduct


  • Install the React DevTools (Chrome (recommended), Firefox)
  • Experience with React and all hooks

System Requirements

  • git v2.13 or greater
  • NodeJS 12 || 14 || 15 || 16
  • npm v6 or greater

All of these must be available in your PATH. To verify things are set up properly, you can run this:

git --version
node --version
npm --version

If you have trouble with any of these, learn more about the PATH environment variable and how to fix it here for windows or mac/linux.


If you want to commit and push your work as you go, you'll want to fork first and then clone your fork rather than this repo directly.

After you've made sure to have the correct things (and versions) installed, you should be able to just run a few commands to get set up:

git clone
cd react-performance
node setup

This may take a few minutes. It will ask you for your email. This is optional and just automatically adds your email to the links in the project to make filling out some forms easier.

If you get any errors, please read through them and see if you can find out what the problem is. If you can't work it out on your own then please file an issue and provide all the output from the commands you ran (even if it's a lot).

If you can't get the setup script to work, then just make sure you have the right versions of the requirements listed above, and run the following commands:

npm install
npm run validate

If you are still unable to fix issues and you know how to use Docker 🐳 you can setup the project with the following command:

docker-compose up

It's recommended you run everything locally in the same environment you work in every day, but if you're having issues getting things set up, you can also set this up using GitHub Codespaces (video demo) or Codesandbox.

Running the app

To get the app up and running (and really see if it worked), run:

npm start

This should start up your browser. If you're familiar, this is a standard react-scripts application.

You can also open the deployment of the app on Netlify.

Running the tests

npm test

This will start Jest in watch mode. Read the output and play around with it. The tests are there to help you reach the final version, however sometimes you can accomplish the task and the tests still fail if you implement things differently than I do in my solution, so don't look to them as a complete authority.


  • src/exercise/ Background, Exercise Instructions, Extra Credit
  • src/exercise/00.js: Exercise with Emoji helpers
  • src/__tests__/00.js: Tests
  • src/final/00.js: Final version
  • src/final/00.extra-0.js: Final version of extra credit

The purpose of the exercise is not for you to work through all the material. It's intended to get your brain thinking about the right questions to ask me as I walk through the material.

Helpful Emoji 🐨 πŸ’° πŸ’― πŸ“ πŸ¦‰ πŸ“œ πŸ’£ πŸ’ͺ 🏁 πŸ‘¨β€πŸ’Ό 🚨

Each exercise has comments in it to help you get through the exercise. These fun emoji characters are here to help you.

  • Kody the Koala 🐨 will tell you when there's something specific you should do version
  • Marty the Money Bag πŸ’° will give you specific tips (and sometimes code) along the way
  • Hannah the Hundred πŸ’― will give you extra challenges you can do if you finish the exercises early.
  • Nancy the Notepad πŸ“ will encourage you to take notes on what you're learning
  • Olivia the Owl πŸ¦‰ will give you useful tidbits/best practice notes and a link for elaboration and feedback.
  • Dominic the Document πŸ“œ will give you links to useful documentation
  • Berry the Bomb πŸ’£ will be hanging around anywhere you need to blow stuff up (delete code)
  • Matthew the Muscle πŸ’ͺ will indicate that you're working with an exercise
  • Chuck the Checkered Flag 🏁 will indicate that you're working with a final
  • Peter the Product Manager πŸ‘¨β€πŸ’Ό helps us know what our users want
  • Alfred the Alert 🚨 will occasionally show up in the test failures with potential explanations for why the tests are failing.


Thanks goes to these wonderful people (emoji key):

Kent C. Dodds

πŸ’» πŸ“– πŸš‡ ⚠️

Justin Dorfman


FrΓ©dΓ©ric Bolvin


Vojta Holik

πŸ’» 🎨

Marco Moretti


Ricardo Busquet


Selwyn Yeow


Emmanouil Zoumpoulakis


Peter HozΓ‘k


Pritam Sangani


Christian Schurr

πŸ’» πŸ“–

Johnny Magrippis



πŸ’» πŸ“–

Robbert Wolfs


Kim Gwan-duk


Rasmus Josefsson


Marcos NASA G


Markus Lasermann


Vasilii Kovalev


Matan Kushner


MichaΓ«l De Boey


Veljko Blagojevic


Bobby Warner


JesΓΊs RodrΓ­guez


Valentin Hervieu


David SΓ‘nchez


Merott Movahedi


Arjen Bloemsma


Naveed Elahi


Tyler Knappe



πŸ’» πŸ“–

Emil Esplund


Justin Stanley


This project follows the all-contributors specification. Contributions of any kind welcome!

Workshop Feedback

Each exercise has an Elaboration and Feedback link. Please fill that out after the exercise and instruction.

At the end of the workshop, please go to this URL to give overall feedback. Thank you!

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