How to generate a local SSL certificate

Note: I ran these commands on macOS. Linux should work in the same way. I don’t guarantee for Windows.

In the project root folder, run:

openssl req -x509 -newkey rsa:2048 -keyout keytmp.pem -out cert.pem -days 365

Now run:

openssl rsa -in keytmp.pem -out key.pem

You should now have the files cert.pem and key.pem in the folder.

With Express/Node.js, you can load the certificate and key using this code:

const fs = require('fs')
const https = require('https')
const app = express()

app.get('/', (req, res) => {
  res.send('Hello HTTPS!')
})

https.createServer({
  key: fs.readFileSync('key.pem'),
  cert: fs.readFileSync('cert.pem')
}, app).listen(3000, () => {
  console.log('Listening...')
})

If you’re using create-react-app, change the start script in the package.json file to:

"start": "export HTTPS=true&&SSL_CRT_FILE=cert.pem&&SSL_KEY_FILE=key.pem react-scripts start",

Look at your framework/library documentation on the instructions on how to pass the certificate and key to the app.