Certbot
Get free HTTPS certificates forever from Let's Encrypt
...It fetches a digital certificate from Let’s Encrypt, an open certificate authority launched by the EFF, Mozilla, and others. This certificate then lets browsers verify the identity of web servers and ensures secure communication over the Web.
Obtaining and maintaining a certificate is usually such a hassle, but with Certbot and Let’s Encrypt it becomes automated and hassle-free. With just a few simple commands, you can turn on and manage HTTPS.
Certbot runs directly on the web server, so make sure to check with your hosting provider first if you are able to use Certbot.