Google To Index HTTPS Pages By Default

Google always worked on making things simpler for users and user security is their topmost priority. A secure web is what many companies in the web world aim for. From last year Google started giving a slight ranking boost to HTTPS URLs  in search results.
 
Google states that while a user in browsing the web, he/she should not be worried about eavesdropping, man-in-the-middle attacks, or data modification. That means the experience should be private and between the user and the website. So, Google announced that they're adjusting there indexing system to look for more HTTPS pages. That is they will start crawling HTTPS equivalents of HTTP pages, even when the former are not linked to from any page.  That said, Google will choose to index HTTPS URL when two URLs from the same domain appear to have the same content but are served over different protocol schemes.
 
Google will choose to index HTTPS URL links if,
  • It doesn’t contain insecure dependencies.
  • It isn’t blocked from crawling by robots.txt.
  • It doesn’t redirect users to or through an insecure HTTP page.
  • It doesn’t have a rel="canonical" link to the HTTP page.
  • It doesn’t contain a noindex robots meta tag.
  • It doesn’t have on-host outlinks to HTTP URLs.
  • The sitemaps lists the HTTPS URL, or doesn’t list the HTTP version of the URL
  • The server has a valid TLS certificate. 
 As stated via official blog,
 
"Although our systems prefer the HTTPS version by default, you can also make this clearer for other search engines by redirecting your HTTP site to your HTTPS version and by implementing the HSTS header on your server."
 
"We’re excited about taking another step forward in making the web more secure. By showing users HTTPS pages in our search results, we’re hoping to decrease the risk for users to browse a website over an insecure connection and making themselves vulnerable to content injection attacks. As usual, if you have any questions or comments, please let us know in the comments section below or in our webmaster help forums."
 
HSTS Settings
Image Source: chrome://net-internals/#hsts