Facebook created and open-sourced the Hack programming language in 2014.
Hack was developed by Facebook for its large PHP codebase and publicly announced in March 2014. It was designed to combine the rapid development style associated with PHP with features such as static typing, which can help developers identify certain errors before code runs.
Hack runs on the HipHop Virtual Machine, commonly called HHVM. Facebook had created HHVM to improve the performance of PHP applications, and Hack was built to work closely with that environment.
Hack is sometimes confused with Rust, Swift, or Kotlin because all are modern programming languages used in software development. Rust was developed by Mozilla, Swift by Apple, and Kotlin by JetBrains. Hack’s origin is specifically tied to Facebook’s engineering organization.