Personal use project.
A simple, drag-and-drop utility for Mac and Windows that compresses massive PS1, PS2, and PSP .ISO and .CUE backups into highly optimized .CHD, .ZSO, or .CSO files with batch conversion suport.
This tool explicitly provides conversion paths tailored for your specific gaming setup:
- CUE / ISO ➔ CHD
- ISO ➔ CSO
- CSO ➔ ZSO
- ISO ➔ ZSO
If you are playing your games on DuckStation (PS1) or PCSX2 (PS2), you should ALWAYS use the CHD format. CHD (Compressed Hunks of Data) uses extremely advanced lossless compression algorithms (like LZMA for data and FLAC for audio) which results in the absolute smallest file sizes possible for CD and DVD based games. It is the gold standard for emulation.
Note
You must have chdman installed on your system to use the CHD conversion option. Mac users can simply run brew install rom-tools in the terminal, or use the button in the application to auto-install it.
Tip
How to compress PS1 Games (BIN/CUE): PS1 games often come with multiple .bin files and one .cue file. To compress them into a single .chd file, ensure all the .bin files are in the exact same folder, and drag and drop ONLY the .cue file into this tool! The engine will automatically read the .cue map, pull in all the associated .bin files, and merge them into one single file.
If you are playing your games on the PPSSPP Emulator (PSP) or PCSX2 Emulator (PS2) (on a PC, Mac, or phone), you should ALWAYS use the CSO format. An uncompressed .ISO file wastes gigabytes of storage space with blank "dummy data". The .CSO format uses standard Zlib compression to aggressively shrink the file down. Because modern PCs and smartphones have massive processing power, the emulator can decompress the CSO file instantly in the background, giving you massive storage savings with absolutely zero performance loss.
Warning
PPSSPP does not currently support the ZSO format.
If you are playing games on Real Physical PSP Hardware (ARK-5) or a Real PS2 Console (OPL), you should ALWAYS use the ZSO format.
Back in the day, people used CSO files on real hardware to save space. However, because Zlib compression is so tight, the processors of the PSP and PS2 would choke trying to decompress the game files fast enough, causing terrible lag spikes and audio stuttering (especially in games like Grand Theft Auto).
The .ZSO format fixes this by using ultra-fast LZ4 compression. It shrinks the game beautifully, but decompresses roughly 500% faster. This allows the physical console to unpack the game instantly, completely curing the lag spikes while still saving you massive amounts of space on your memory stick!
To ensure your compressed games boot flawlessly, please verify that your hardware or emulator meets the following requirements:
- Real PSP Console: Must be running ARK-4 or ARK-5 Custom Firmware (CFW). Older firmwares like PRO-C or ME do not support ZSO natively out of the box.
- Real PS2 Console: Must be using OPL (Open PS2 Loader) v1.2.0 Beta or newer. Older stable builds of OPL (like v1.1.0) do not have the ZSO decompression engine built-in.
- PS1 Emulation: Fully supported by DuckStation, RetroArch (SwanStation/Beetle cores), and most modern emulators.
[!IMPORTANT] Cannot be used on real PS1 hardware without extracting back to
.bin/.cueand burning to a CD-R. - PS2 Emulation: Fully supported by PCSX2 (Nightly builds / v1.7+).
[!WARNING] RPCS3 (PS3 Emulator) does not support CHD.
- PSP Emulation: Fully supported by the PPSSPP emulator on all platforms (PC, Mac, Android, iOS).
- Real PSP Console: Supported by virtually all legacy Custom Firmwares (PRO, ME) and modern ones (ARK).
[!TIP] ZSO is highly recommended over CSO for real hardware to prevent lag.
If you prefer to use the command line, or if you are on Windows, you can install the interactive Terminal User Interface (TUI) directly to your system path.
macOS Installation: Open your Terminal and run the following command:
curl -sL https://github.com/wako69420/iso-compressor/releases/latest/download/install_mac.sh | bashWindows Installation: Open PowerShell and run the following command:
irm https://github.com/wako69420/iso-compressor/releases/latest/download/install_win.ps1 | iexOnce installed on either OS, simply type the following command into any terminal to launch the menu, where you can select Batch Compress a Folder or compress individual files via Drag-and-Drop:
iso-compressor- Download the latest Release from the Releases tab.
- Open the app by double-clicking it to access the Main Menu, or simply drag-and-drop your
.ISO/.CSOfiles (or an entire folder) directly onto the app icon. - You can choose to compress a Single File, or use Compress Folder (Batch) to automatically process an entire directory of games sequentially!
- A prompt will clearly ask you to choose between CHD (For PS1/PS2 Emulators), CSO (For PSP Emulators), or ZSO (For Real Hardware).
Development on this project is active. Expect some QOL improvements, deeper automation, wider format/console support and Linux support in the upcoming releases.
This project is licensed under the BSD 3-Clause License.
- maxcso Engine: All core compression credit goes to unknownbrackets for the blazing fast CSO/ZSO engine. (Licensed under ISC).
- MAME Team (chdman): MAME Development Team (and Aaron Giles) for the CHD format and the
chdmantool. (Licensed under GPL-2.0 / BSD-3-Clause). - ARK-5 Custom Firmware: ARK-5 Team (Acid_Snake, KrazyS, and contributors) native ZSO (Inferno V2) support directly into the firmware.
- OPL (Open PS2 Loader): The OPL Development Team
batch-conversion, roms, rom-hacks, handhelds, retro-gaming, emulation, playstation, ps1, ps2, psp, chd, cso, zso, iso, pcsx2, duckstation, ppsspp, opl, ark-5, maxcso