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CSO ZSO
File conversion

Convert CSO to ZSO

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Is it possible to convert CSO to ZSO?
Yes - CSO converts to ZSO.

Re-compress to the ZSO (LZ4) variant for faster decompression on weak hardware (some handhelds), at a slightly larger size. maxcso writes ZSO directly ('maxcso --format=zso').

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Tested on macOS, Windows & Linux
Last verified Nov 2026

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How to convert CSO to ZSO

Converting a .CSO file to .ZSO lets you open the content in software that prefers the .ZSO format, though some details may change compared with the original. We are still putting together the list of programs that handle .CSO files.

A full step-by-step guide for this conversion is on the way; the information above is drawn straight from our database.

About these formats

.CSO CISO Compressed ISO Image

A CSO file is a compressed PSP (or PS2) game disc image - an ISO with each block DEFLATE-compressed to save space on a memory stick. Open it directly in the PPSSPP emulator…

Open .CSO details →
.ZSO ZSO File

A .ZSO file is a data file used by specific software.

Open .ZSO details →