How to add HTTPS listener to EC2 ALB

In addition to what Riku said, you can also create a self-signed certificate, and then import that into ACM, and deploy that to your ALB Listener.

You can do this directly with OpenSSL on MacOS or on Linux as follows:

openssl req -x509 -nodes -days 365 -newkey rsa:2048 -keyout /etc/ssl/private/my-selfsigned.key -out /etc/ssl/certs/my-selfsigned.crt

Then you can import the certificate to ACM using the CLI as follows:

$ aws acm import-certificate --certificate fileb://etc/ssl/certs/my-selfsigned.crt --private-key fileb://etc/ssl/private/my-selfsigned.key

You may need to change the file-paths depending on where your certificate and key is. Refer to the documentation on exactly how to do this: https://docs.aws.amazon.com/acm/latest/userguide/import-certificate-api-cli.html#import-certificate-cli

Once you have done this - the self-signed certificate can be used on an ALB.

Note with imported certificates - you need to take care of renewing them - so Riku's advice to get a real domain is the most robust way forward in production. Self signed certificates are not generally trusted by most client machines.