6 file types use the .pac file extension.

What is a PAC file?

A PAC file is a configuration file used by web browsers to select an appropriate proxy server . It contains one or more JavaScript functions with one of them named FindProxyForURL , which defines rules for choosing a proxy server based on a given URL . PAC files are used for controlling and load-balancing Internet traffic, especially in corporate environments.

More Information

Category: Web Files

PAC Subtitles File

Proprietary subtitles format created by Screen Subtitling Systems; used for synchronizing closed captions with a video timeline; can be edited with subtitle editing software such as EZTitles and converted to more standard formats, including .SRT and .SUB .

Programs that open PAC files

Updated: February 7, 2018

Hedgehog Engine 3D Model

A PAC file may also be a 3D model used in a video game developed by SEGA or Sonic Team. Notably, the games Sonic Forces and Sonic Lost World use 3D models saved as PAC files.

PAC files are 3D models used in games that use the Sonic Team's Hedgehog Engine game engine. In addition to Sonic Forces and Sonic Lost World, Puyo Puyo Tetris 2, Sakura Wars, Mario & Sonic at the Olympic Games Tokyo 2020, Mario & Sonic at the Rio 2016 Olympic Games, and Olympic Games Tokyo 2020 - The Official Video Game use PAC files.

Most players who play these games will never encounter the games' PAC files. However, some enthusiastic modders have created tools that allow them to extract, edit, and create their own PAC files.

You can use HedgeLib (cross-platform) to extract PAC files from a Hedgehog Engine game. Then, you can use Noesis (Windows) to open the files' contents and convert them to other 3D model formats.

After you've finished editing your PAC file, you can use HedgeLib to repackage the file and insert it into a Hedgehog Engine game.

Programs that open or reference PAC files

Updated: September 7, 2021

SBStudio II Song File

A PAC file may also be a song created by SBStudio II, a music composition program developed by Henning Helstrom for DOS-based systems in the 1990s. It contains the musical arrangement and the audio samples used in a composition. SBStudio II users create, edit, and save songs in the PAC format, then load them later for playback or further editing within the program.

The PAC format comprises several blocks that store various pieces of information, including instrument samples, pattern data, and playback settings, which enables SBStudio II to load an entire song from a single file. Because the file stores multiple types of data in a single file structure, users often refer to PAC files as “package” files.

NOTE: Today, PAC files are obscure since SBStudio II, and the format is no longer developed. The files are primarily of interest to enthusiasts who preserve or convert vintage music files from older DOS-era trackers.

You can open PAC files with FMJ-Software Awave Studio in WIndows. To open a KRZ file with FMJ-Software Awave Studio, select File → Open .

Programs that open PAC files

Updated: July 11, 2025

STAD Graphic File

Image format used by the STAD program for Atari ST systems; saved as a black and white image with a resolution of 640x400 pixels; considered a high-resolution graphic for Atari computers.

Programs that open PAC files

Updated: February 24, 2010

WWE 2K Game Data Archive

A PAC file may also be an archive that contains game data used by a game in the WWE 2K series. For example, it may contain game audio, animations, textures, and/or character models. Modders have created tools that allow them to decompress and extract data from PAC files.

WWE 2K is a series of pro wrestling video games. Prior to WWE 2K20, games in the series were developed by Yuke's. These entries store various types of game data in PAC files.

Although PAC files are not meant to be opened by players, WWE 2K modders have developed tools that allow them to extract the data the files contain. Modders can also use these tools to add files to existing PAC files, to insert custom audio, animations, and characters into a game.

You can use PAC Editor (Windows) or rePac (Windows) to view and extract the files a PAC file contains.

Programs that open PAC files

Updated: November 22, 2022