What language was used in Facebook?

Answer 1

https://www.sololearn.com/Discuss/23112/?ref=app
This may be helpful.

However Facebook is made with PHP, Javascript for the Front-End, Java and C++ for the back-end (as far as I know).

Please next time use the search bar before asking.

Maybe someone else has made your same question before.

Answer 2

you can google that:

https://www.pingdom.com/blog/the-software-behind-facebook/