The actual compressed game data, typically handled in 2,048-byte sectors. The Trade-off: Compression vs. Performance

The (available on Windows, macOS, Linux, Android, iOS, and even Xbox) is the gold standard for playing CSO PSP archives. Here’s how to get the best experience:

Once you have your CSO file, you'll need to know how to use it depending on your setup.

This command takes your standard game.iso file and outputs a compressed game.cso file in the same directory. For most users, this simple command is all you need.

A key feature of the CSO format is its , where a setting of "1" is the fastest (least compression) and "9" is the slowest (most compression).

Click and select the PSP ISO file you want to compress. Click the Save button in the top menu.

PPSSPP reads CSO files natively with zero performance degradation on almost all modern devices. Best Practices for Digital Archiving

If you play PSP games on modern hardware using the emulator (on PC, Android, iOS, or Steam Deck), CSOs are fully supported. Modern processors handle on-the-fly decompression effortlessly, meaning you get all the space-saving benefits of CSOs with absolutely zero performance penalties. Understanding Compression Levels

Dump your UMD using Custom Firmware on a PSP. Hold the R-trigger on boot to enter the Recovery Menu, enable "USB device: UMD," then plug into your PC. Copy the UMD.ISO file.

Digital backups protect against "disc rot" and the physical failure of aging UMD drives.

Building a clean, playable archive is better than downloading random files from untrusted sites. Here’s the safe, ethical approach.

Ensure your game backups are clean, uncompressed .iso files.

A great archive is an organized archive. Follow these tips to keep your retro collection pristine: