Garry's Mod Addon

File Format
Name	Garry's Mod Addon
Ontology	Electronic File Formats Game data files Garry's Mod Addon
Extension(s)	.gma
Released	2010

Garry's Mod Addon files are used in the PC game Garry's Mod for storing downloadable game content. They store game files in a hierarchy of folders, so gma files can be created from a folder, or extracted into a hierarchy of folders.

Format

char[4] ident ("GMAD")

uint8 version

uint64 steam_id (unused)

uint64 timestamp

uint8 zero (0)

char addon_name (null terminated string of variable size)

char addon_description (null terminated string of variable size)

char addon_author (null terminated string of variable size) ("Author Name")

uint32 addon_version

struct file_table

uint32 file_number

char file_path (null terminated string of variable size)

uint64 file_size

uint32 file_crc

uint32 zero (0)

struct files

byte file (file data based on information from the file table)

uint32 addon_crc

Links

• How to create and extract gma files
• Source code for gmad to create and extract gma files