In 2011, Google introduced HTTPS by default on its popular Gmail service.
Yahoo moved all its users' data to secure servers in March 2014, and Facebook committed to secure browsing by default since July 2013.
The move of larger tech companies to encourage encryption comes after the leaks from Edward Snowden alleged that the National Security Agency (NSA) and GCHQ used various technologies to spy on citizens, which prompted a global debate about cyber-security and privacy.