More than one million people are now connecting to Facebook through Tor "dark Web" - which maintains privacy and leaves no digital trail - every month, media reports said on Saturday.
According to Facebook, the growth of Tor over the past few years has been "roughly" linear, noting that some 525,000 people who accessed the service via Tor in June 2015 rose to more than one million in April this year.
"This [Tor] growth is a reflection of the choices that people make to use Facebook over Tor, and the value that it provides them. We hope they will continue to provide feedback and help us keep improving," TechCrunch quoted Facebook as saying.
Tor allows anonymous Web browsing by sending data through multiple encrypted steps rather than making direct connections that shields the identity of its users.
Facebook created a dedicated address for Tor access in October 2014, making it easier for users to connect via Tor and give them privacy.
Facebook also expanded its Tor support at the start of this year by rolling out support for the Android Orbot proxy, giving Android Facebook users an easier way to use Tor. Apple's iOS platform still does not have Tor support.
Confirming Facebook's claim, a spokeswoman for Tor said in a statement: "When using Facebook website over Tor, Tor Browser is in charge of that data, so it is anonymous. Of course, someone may post a status update saying that they are at some restaurant, for instance, and that would de-anonymise them."
Tor could be used in countries where internet access or use of Facebook is blocked or censored, the Tor statement added.
"Many people use Tor in countries where the internet is censored, not in order to be anonymous. Tor allows them to access the uncensored internet, including reaching Facebook. In Iran, for instance, Facebook is blocked. So people use Tor to get onto the internet and browse and from there they can reach Facebook," it read.
Privacy activists, hackers, activists and journalists use this "dark Web" to communicate securely.