Hack Standard Library

:::info[Note] This is a point-in-time snapshot of the API documentation from January 2026. Going forward, we will not be maintaining a public copy of these references, and recommend users to refer to the built-in signature helpers available in the Hack LSP instead for complete and up-to-date information. :::

Classes

• HH\Lib\Async
• HH\Lib\File
• HH\Lib\IO
• HH\Lib\OS
• HH\Lib\Regex
• HH\Lib\TCP
• HH\Lib\Unix

Functions

• HH\Lib\C
• HH\Lib\Dict
• HH\Lib\File
• HH\Lib\IO
• HH\Lib\Keyset
• HH\Lib\Legacy_FIXME
• HH\Lib\Locale
• HH\Lib\Math
• HH\Lib\OS
• HH\Lib\PseudoRandom
• HH\Lib\Regex
• HH\Lib\SecureRandom
• HH\Lib\Str
• HH\Lib\TCP
• HH\Lib\Unix
• HH\Lib\Vec

Interfaces

• HH\Lib\File
• HH\Lib\IO
• HH\Lib\Network
• HH\Lib\OS
• HH\Lib\Str
• HH\Lib\TCP
• HH\Lib\Unix

Traits

• HH\Lib\IO