Facebook has implemented HSTS preloading that instructs a browser to always use SSL/TLS to communicate with eligible websites.

Facebook has upgraded its link security infrastructure to include HTTP Strict Transport Security (HSTS) preloading that instructs a browser to always use SSL/TLS to communicate with eligible websites.

Facebook and Instagram links will automatically update from HTTP to HTTPS for eligible websites.

“We have recently upgraded our link security infrastructure to include HSTS preloading, which automatically upgrades HTTP links to HTTPS for eligible websites. This will improve people’s security and will also often improve the speed of navigation to sites from Facebook.” reads the announcement published by Facebook.

According to Facebook, the modification aims to improve security and navigation speed for Facebook and Instagram links.

Facebook determines the links that are eligible for HTTPS based on two sources:

The Chromium preload list, that is currently used in most major browsers;

Recording HSTS headers from sites shared on Facebook, in this case, the browser preload list is updated with any sites that serve HSTS with the preload directive.

Facebook invites websites to support HTTPs and sponsors Let’s Encrypt initiative which provides free TLS certificates and instructions on how to enable HTTPS for most common server software.

Pierluigi Paganini

(Security Affairs – HTTPS, HSTS Preloading)