# What is Hack?

Hack is a programming language for [HHVM](http://hhvm.com) that interoperates
seamlessly with PHP.  Hack reconciles the fast development cycle of PHP with the
discipline provided by static typing, while adding many features commonly found
in other modern programming languages.

Hack provides instantaneous type checking via a local server that watches the
filesystem. It typically runs in less than 200 milliseconds, making it easy to
integrate into your development workflow without introducing a noticeable delay.

For more information, see the [website](http://hacklang.org/).
