[reactjs] How to specify a port to run a create-react-app based project?

My project is based on create-react-app. npm start or yarn start by default will run the application on port 3000 and there is no option of specifying a port in the package.json.

How can I specify a port of my choice in this case? I want to run two of this project simultaneously (for testing), one in port 3005 and other is 3006

In Windows it can be done in 2 ways.

1. Under " \node_modules\react-scripts\scripts\start.js" , search for "DEFAULT_PORT" and add the desire port number.

   E.g : const DEFAULT_PORT = parseInt(process.env.PORT, 10) || 9999;

2. In package.json , appent the below line. "start": "set PORT=9999 && react-scripts start" Then start the application using NPM start. It will start the application in 9999 port.

Just update a bit in webpack.config.js:

devServer: {
    historyApiFallback: true,
    contentBase: './',
    port: 3000 // <--- Add this line and choose your own port number
}

then run npm start again.

It would be nice to be able to specify a port other than 3000, either as a command line parameter or an environment variable.

Right now, the process is pretty involved:

1. Run npm run eject
2. Wait for that to finish
3. Edit scripts/start.js and find/replace 3000 with whatever port you want to use
4. Edit config/webpack.config.dev.js and do the same
5. npm start

just run below command

PORT=3001 npm start

You can specify a environment variable named PORT to specify the port on which the server will run.

$ export PORT=3005 #Linux
$ $env:PORT=3005 # Windows - Powershell

Create a file with name .env in the main directory besidespackage.json and set PORT variable to desired port number.

For example:

.env

PORT=4200

You can find the documentation for this action here: https://create-react-app.dev/docs/advanced-configuration

How about giving the port number while invoking the command without need to change anything in your application code or environment files? That way it is possible running and serving same code base from several different ports.

like:

$ export PORT=4000 && npm start

You can put the port number you like in place of the example value 4000 above.

Why not just

PORT=3030 npm run start

This works on both Windows and Linux (Doesn't work on Mac)

package.json

"scripts": {
    "start": "(set PORT=3006 || export PORT=3006) && react-scripts start"
    ...
}

but you propably prefer to create .env with PORT=3006 written inside it

This worked for Linux Elementary OS

"start": "PORT=3500 react-scripts start"

Here is another way to accomplish this task.

Create a .env file at your project root and specify port number there. Like:

PORT=3005

you can find default port configuration at start your app

yourapp/scripts/start.js

scroll down and change the port to whatever you want

const DEFAULT_PORT = parseInt(process.env.PORT, 10) || 4000;

hope this may help you ;)

Changing in my package.json file "start": "export PORT=3001 && react-scripts start" worked for me too and I'm on macOS 10.13.4

In case you have already done npm run eject, go to scripts/start.js and change port in const DEFAULT_PORT = parseInt(process.env.PORT, 10) || 3000; (3000 in this case) to whatever port you want.

Try this:

npm start port=30022

To summarize, we have three approaches to accomplish this:

1. Set an environment variable named "PORT"
2. Modify the "start" key under "scripts" part of package.json
3. Create a .env file and put the PORT configuration in it

The most portable one will be the last approach. But as mentioned by other poster, add .env into .gitignore in order not to upload the configuration to the public source repository.

More details: this article

In your package.json, go to scripts and use --port 4000 or set PORT=4000, like in the example below:

package.json (Windows):

"scripts": {
    "start": "set PORT=4000 && react-scripts start"
}

package.json (Ubuntu):

"scripts": {
    "start": "export PORT=4000 && react-scripts start"
}

For my windows folks I discovered a way to change ReactJS port to run on any port you want.Before running the server go to

 node_modules/react-scripts/scripts/start.js

In it, search for the line below and change the port number to your desired port

 var DEFAULT_PORT = process.env.PORT || *4000*;

And you are good to go.

You could use cross-env to set the port, and it will work on Windows, Linux and Mac.

yarn add -D cross-env

then in package.json the start link could be like this:

"start": "cross-env PORT=3006 react-scripts start",