Why Google shows some https and some without?

[markku]

If you google for site:xenforo.com, you'll see that some search results have https://xenforo.com, while others have only xenforo.com, omitting the https:// (even though it links to https://, it doesn't show it in the result as such)

What's the logic here?

 

[TPerry]

What's the logic here?

The logic is probably that for a long time XenForo site was not SSL secured and those links are from that period? The fact that it links to the SSL version only means that the HTTP server is forcing a HTTP -> HTTPS rewrite.