Files with cso extension are in most cases disk images saved in a common disk format for Sony Playstation. Very often used for backups of game disks. CSO format needs a special customized firmware so PSP can read them.

There is one other file type using
the CSO file extension!

empty icon.cso - Compiled Shader Object

Detailed description

Software that open cso file

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CSO file extension - CISO compressed ISO image

What is cso file? How to open cso files?

File type specification:

Archive and compressed file type icon Archive and compressed file type

cso file icon: cso filetype icon

File extension cso is used for compressed ISO images. They are often used as a medium to play PSP games. The standard medium used by Sony PlayStation Portable is Universal Media Disc (UMD).

CSO format has nine levels of compression. Higher levels mean better compression, but slower loading times of compressed ISOs.

These cso files are created by PSP ISO Compressor.

CSO CISO compressed ISO file allows playing PSP games from memory card, but PSP must have installed user customized firmware, that includes support to reading of cso files.

Updated: November 24, 2023

The default software associated to open cso file:

PSP ISO Compressor picture or screenshot

PSP ISO Compressor  Microsoft Windows software

Company or developer:

A front end converter for Windows, PSP ISO Compressor supports several ISO compression formats -- CSO, DAX, and the newly introduced JSO.


Related articles:

Run PSP games on PC

Help how to open:

The *.cso file is compressed ISO image file and can be opened in SONY PlayStation Portable, that has installed user customised firmware with support to open the CSO CISO compressed ISO file.

How to convert:

PSP ISO Compressor supports conversion of *.cso files in to other disk file formats.

Find conversions from cso file:

cso to dax

cso to iso

cso to jso

Find converter to cso file type:

dax to cso

iso to cso

jso to cso

File identification strings:

HEX code: 43 49 53 4F

Related links:

PSP emulators for PC at The Emulator Zone

List of software applications associated to the .cso file extension

Recommended software programs are sorted by OS platform (Windows, macOS, Linux, iOS, Android etc.)
and possible program actions that can be done with the file: like open cso file, edit cso file, convert cso file, view cso file, play cso file etc. (if exist software for corresponding action in's database).

Click on the tab below to simply browse between the application actions, to quickly get a list of recommended software, which is able to perform the specified software action, such as opening, editing or converting cso files.

Software that open cso file - CISO compressed ISO image

Programs supporting the exension cso on the main platforms Windows, Mac, Linux or mobile. Click on the link to get more information about listed programs for open cso file action.

Microsoft Windows:

Apple macOS / Mac OS X:


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