PAK

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PAK file formats are package formats previously used by GoldSrc engine games to store content. It was first introduced in Quake engine which GoldSrc subsequently adopted it. Unlike Quake, GoldSrc prioritizes loose files over those found in a PAK.

This was changed during the WON/Retail to Steam transition in 2003, when the game files were stored inside GCF files located in ...\Steam\steamapps\username\ folder. Since the 2013 SteamPipe update, the game file have been stored directly to the filesystem (example: ...\SteamApps\common\Half-Life\valve), as opposed to Source and Source 2 engines (which continued to packing game files inside multiple VPK files after SteamPipe transition) as most modern systems are fast enough to load GoldSrc game files quickly.

As of today, the Steam version of Half-Life, along with other GoldSrc games are still able to load the .pak file despite longer being used to store vanilla game files.

Important:PAK is often used as a generic file extension in the industry. PAK files used by other software, such as Chromium, Unreal Engine 4+, or CryEngine are completely unrelated to the file format used by GoldSrc and id Tech 2.

Note:MP3 files cannot be packaged in a PAK file.

Confirm:This might also be the case for WebM, and formerly AVI.

Structs

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This work is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License; version 2 as published by the Free Software Foundation. This work is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See version 2 of the GNU General Public License for more details.

 C code from common/qfiles.h in the original Quake II development tools:

#define IDPAKHEADER		(('K'<<24)+('C'<<16)+('A'<<8)+'P')

typedef struct
{
	char	name[56];
	int		filepos, filelen;
} dpackfile_t;

typedef struct
{
	int		ident;		// == IDPAKHEADER
	int		dirofs;
	int		dirlen;
} dpackheader_t;

#define	MAX_FILES_IN_PACK	4096

Todo: Explain what the variable names mean, and how the structs are laid out in a PAK

Important:MAX_FILES_IN_PACK is an engine limit, not a format one. The 2023 Kex remaster of Quake II exceeds MAX_FILES_IN_PACK, and as such will not load in some tools such as PakScape.

See also

• VPK - Package format used by Source and Source 2
• GCF - Package format used by Steam prior to SteamPipe
• HLLib - Library which can load PAK files
• VPKEdit - Program which can create and modify PAK files
• PakScape - Ditto
• PakExplorer - Ditto