On the main interface, select your desired action from the radio buttons on the left panel (e.g., ).
Highly compressed CSO files (Level 9) require the PSP CPU to decompress data on the fly. If audio cuts out or frame rates drop, re-compress the original ISO using . "C1-2858-3" or Error Codes on PSP
, allowing you to fit more games onto a single memory stick. Key Features of Version 1.4 Format Versatility
If you are a proud owner of a PlayStation Portable (PSP) or a dedicated emulation enthusiast running PPSSPP on your smartphone or PC, you know the golden rule of retro gaming:
| Tool | Interface | Key Feature | Platform | Best For | | :--- | :--- | :--- | :--- | :--- | | | Graphical (GUI) | Supports ISO, CSO, DAX, and JSO; includes decompression. | Windows | Beginners and users who need a simple, all-in-one GUI. | | UMDGen v4.00 | Graphical (GUI) | Edits ISO contents, removes unnecessary files (updates/demos), and compresses to CSO. | Windows | Advanced users who want to manually "shrink" a game by deleting filler content. | | YACC (Yet Another CSO Compressor) | Graphical (GUI) | A popular tool dedicated to converting ISO to CSO with a focus on simplicity. | Windows | Users focused primarily on CSO compression. | | CisoPlus! | Command-Line | An enhancement of Booster's original CSO code; offers a simulation mode to preview compression ratios. | Cross-platform | Users comfortable with command-line tools who want extra control and estimation features. | | maxcso | Command-Line | A modern, fast compressor that uses multiple algorithms (including LZ4) and can utilize all CPU cores for speed. | Cross-platform (Unix/Linux, macOS) | Power users and emulation enthusiasts on modern systems seeking maximum speed and efficiency. |
Right-click the .zip file and select using Windows Explorer, WinRAR, or 7-Zip.
When the process is complete, navigate to your output folder. You will find your new, smaller .CSO (or .JSO / .DAX ) file. Copy this file to the ISO folder on your PSP's Memory Stick (if using custom firmware) or load it directly into the PPSSPP emulator. It should work just like the original ISO file!
PSP ISO Compressor v1.4 is a portable application. It runs directly from the extracted folder without making changes to your Windows registry. Step-by-Step Guide: How to Compress an ISO to CSO
The application functions as a multi-format converter, primarily targeting the compression of files into CSO (Compressed ISO) and DAX formats.
[ Input .ISO ] ──> [ Select Compression Level (1-9) ] ──> [ Output .CSO ] Follow these instructions to shrink your games: Launch [1].
Click the browse button next to the "Input File(s)" field and select the PSP .ISO game file you want to compress.
Features a sliding scale from Level 1 (minimal compression, less lag) to Level 9 (maximum compression, potential for in-game stuttering).
Are you playing games on an or using the PPSSPP emulator ?
