PCSX2 is the gold standard for PS2 emulation. For a long time, it didn't support CHD natively.
For example:
As of PCSX2 Nightly builds (version 1.7+), CHD support is baked in. game ps2 chd free
CHD compression shrinks PS2 ISO files by roughly 30% to 60% depending on the game.
However, because millions of physical PS2 discs exist, the retro community focuses on converting your personal ISOs to CHD—which is completely free. PCSX2 is the gold standard for PS2 emulation
Go to the official MAME dev website and download the latest release. Extract the ZIP folder. Locate the chdman.exe file. Step 2: Create a Batch Conversion Script
If you already have a collection of ISO files and want to save space, you don't need to download them again. You can convert them yourself using a tool called chdman. CHD compression shrinks PS2 ISO files by roughly
Up to 65% more hard drive space for more games. How to Convert PS2 ISO to CHD for Free
A 4GB ISO file can often be compressed into a 1GB–2GB CHD file.
The CHD format was originally created by the MAME (Multiple Arcade Machine Emulator) developer team. It is a lossless compression format designed specifically for disc-based media.