Option 1
If you do not need to use Authentication you can add configs to ngrok commands
ngrok http 9000 --host-header=rewrite
or
ngrok http 9000 --host-header="localhost:9000"
But in this case Authentication will not work on your website because ngrok rewriting headers and session is not valid for your ngrok domain
Option 2
If you are using webpack you can add the following configuration
devServer: {
disableHostCheck: true
}
In that case Authentication header will be valid for your ngrok domain