React recently introduced an experimental profiler API. This page gives instructions on how to use this API in a production release of your app.
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React DOM automatically supports profiling in development mode for v16.5+, but since profiling adds some small additional overhead it is opt-in for production mode. This gist explains how to opt-in.
Creating a profiling build can be done by specifying an additional --profile flag:
yarn build --profile
npm run build -- --profileAt the moment, the only way to permanently enable production profiling in CRA apps is to eject. Then you can follow the instructions below and apply these changes to config/webpack.config.prod.js in your app folder.
However, you can also enable profiling temporarily without ejecting.
If you only want to profile the application locally in production mode, you can do this by editing node_modules directly.
Follow the instructions below, and apply them to node_modules/react-scripts/config/webpack.config.prod.js. Then you can run yarn build or npm run build to get a profiling build. Note that your changes would be temporary and will not persist between re-runs of your package manager.
To enable profiling in production mode, modify Webpack configuration file (config/webpack.config.prod.js) as shown below.
module.exports = {
// ...
resolve: {
// ...
alias: {
// ...
'react-dom$': 'react-dom/profiling',
},
// ...
},
// ...
};Note that if you're using a version of
react/react-domthat's less than 16.6, you should refer to this earlier revision of the documentation instead.
Note that if you're using the
schedulepackage v0.3.0-v0.4.0 you should refer to this earlier revision of the documentation instead.
When profiling locally, you might want to disable function name mangling so that you can see the component names in the profiler. Note that this will significantly increase your bundle size so only do this during local development! To do this, find the mangle option for UglifyJSPlugin in the config, and set it to false. Don't forget to undo your changes before a real deployment.
If you are using Webpack 4 to bundle your apps, add the following import aliases to your production config:
module.exports = {
//...
resolve: {
alias: {
'react-dom$': 'react-dom/profiling',
}
}
};Note that if you're using a version of
react/react-domthat's less than 16.6, you should refer to this earlier revision of the documentation instead.
Note that if you're using the
schedulepackage v0.3.0-v0.4.0 you should refer to this earlier revision of the documentation instead.
When profiling locally, you might want to disable function name mangling so that you can see the component names in the profiler. Note that this will significantly increase your bundle size so only do this during local development! To do this, find the mangle option for UglifyJSPlugin in the config, and set it to false. Don't forget to undo your changes before a real deployment.
Performance impact is minor: 4 additional fiber attributes, some additional calls to
peformance.now()within profiled subtrees.The memory impact of the additional fiber attributes should be minor, but will always be there if you're loading the profiling build- so only load it if you're using the data.
The calls to
peformance.now()aren't done unless you're within a part of the tree wrapped with a<Profiler>tag so the CPU impact- minimal either way- would not apply to parts of your app that aren't being profiled.