Click "Convert" or "Compress" and wait for the process to finish.

Always start with verified, clean dumps (such as those from the Redump project) to ensure your conversions are free of bugs, glitches, or data corruption.

An archive of CSO files allows you to preserve your entire PSP catalog in a fraction of the original storage space without sacrificing playability. What is a CSO PSP Archive?

The CSO format is a sector-based compression method that uses the algorithm. Unlike standard ZIP or RAR archives, which must be fully decompressed to be read, CSO allows for "on-the-fly" decompression of specific data blocks.

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

If you have a large ISO file and want to make it a smaller CSO to save space, you need a compression tool.

When archiving games, compression tools offer nine different compression levels. Choosing the right level is a balance between file size and system performance.

Not every PSP game exists as a UMD. Many were digital downloads from the PlayStation Store, saved as EBOOT.PBP files. These can be played directly on PPSSPP by simply copying them over. The EBOOT.PBP format was also used to convert PS1 games for play on the PSP using a tool called .

They allow users to play their library via emulators like PPSSPP or directly on hardware via modern, high-capacity microSD-to-Pro Duo adapters.

At its core, a CSO file is a "Compressed ISO." Its name is an abbreviation of the term "Compressed ISO," reflecting its primary function: shrinking the size of a standard PSP ISO image to save storage space. Developed by a programmer known as Booster, the CSO format was the first major solution created specifically to compress ISO images, and it quickly became a standard for PSP and PS2 disc images, aiming to reduce the pressure on storage.

Higher compression levels result in slower loading. Use level 5-7 for games where load times are critical.

CSO (Compressed ISO) file is a compressed disk image format specifically designed to reduce the size of PlayStation Portable (PSP) game archives while remaining playable. Overview of CSO Files