ReactDevTools V3

# Checkout the extension source
git clone https://github.com/facebook/react-devtools

cd react-devtools

# Checkout the previous release branch
git checkout v3

# Install dependencies and build the unpacked extension
yarn install
yarn build:extension

# Follow the on-screen instructions to complete installation


After this, 
Go to Extensions, Load Unpacked
Point to react-devtools, shells, chrome, unpacked 
Basically, go to folder with a manifes.json


Run in ReactJS - yarn run test:firefox