Think of a standard ISO file as an exact, unaltered copy of a game disc. It includes everything: the game data, audio tracks, video files, and even large sections of blank "dummy data" that were added to optimize disc reading speeds for the original console's laser.
for %%i in (*.iso) do chdman createdvd -i "%%i" -o "%%~ni.chd" ps2 chd roms
This is the headline feature. By removing redundant data and using advanced compression, CHD files are significantly smaller than their ISO counterparts. A typical PS2 game can be reduced from 4.3GB to between 1.8GB and 2.5GB, achieving an average compression rate of 40-58%. This means you can often double or even triple the number of games you can store on a single hard drive or SD card. Think of a standard ISO file as an
The modern iterations of the PCSX2 emulator—versions (including all 2.x releases)—offer native, direct support for CHD files . You do not need to extract or mount the file. You simply direct PCSX2 to the folder containing your CHD files, and the emulator recognizes them instantly. This support extends across nearly all platforms, including dedicated handhelds like the Steam Deck and the Android port AetherSX2. By removing redundant data and using advanced compression,
The situation on Android is a bit nuanced. The popular AetherSX2 project is no longer in active development, but its community-maintained successor, NetherSX2, is the way to go. Both can run CHD files, but you need to be aware of a specific bug.
The tool used for this conversion is chdman , which is part of the MAME suite. While it is a command-line tool, it is straightforward to use. Method 1: Command Line (Windows/Linux/Mac)