Hyper Text Transfer Protocol Secure (HTTPS) is the secure version of HTTP, the protocol over which data is sent between your browser and the website that you are connected to. The 'S' at the end of HTTPS stands for 'Secure'. It means all communications between your browser and the website are encrypted.Now recently Google announced that Blogger or Blogspot will no longer get the setting to change HTTP to HTTPS inside Blogspot because they are permanently moving their HTTP protocol into HTTPS feature. It means that after April each and every Blogspot user will get permanent HTTPS feature.
Here you can see the notice or announcement from Google. If you want to read the previous release of the HTTPs feature then you can go through below article.