The social network made the announcement today stating:
These changes are part of a broader shift in how browsers and web sites encrypt traffic to protect the contents of online communications.
SHA-1 was one of the most widely used digest algorithms on the Web, but it was determined to be less secure than previously believed by a report from the CA/Browser Forum in 2011 on Baseline Requirements for SSL.
The report stated its value had deprecated and recommended that Certificate Authorities move away from SHA-1 to SHA-2 certificate signatures instead.
Google began the process last year and now Facebook is following suit.
Facebook suggests developers check that their apps, SDKs and devices support the SHA-2 standard already.