A newer, highly efficient format gaining popularity in the emulation community for its high compression ratios and ease of use in multi-emulator frontends. Running Compressed Games
Recommended for PCSX2 users. You can use tools like 7-Zip to right-click an ISO, select "Add to archive," and choose the GZIP format with "Ultra" compression.
These involve removing "dummy" files or lower-priority data, such as high-bitrate cutscenes or background music, to reduce the footprint further.
Modern emulators like PCSX2 allow you to play games directly from compressed formats, saving you the trouble of manual extraction. Compression Methods
A standard ISO file is a sector-by-sector copy of a physical disc, including the file system and "padding"—empty data (often just zeros) used by developers to fill the disc and improve reading speeds on original hardware. "Highly compressed" versions use various methods to eliminate this excess:
Popular for handhelds and some homebrew. Software like MaxCSO is specifically designed for PS2 games and is compatible with various loaders.