Open PCSX2 (or your emulator of choice), navigate to your ISO selector, and choose the newly extracted file.
Unlike .zip or .rar files, which must be fully extracted before playing, the PCSX2 emulator can read .chd files directly.
Certain games see massive size reductions with minimal visual impact. These are the best candidates for highly compressed ISOs.
The PS2 was the first console to popularize the DVD format, with many games easily exceeding 1 GB to 4.7 GB. For modern emulators like on Android or PCSX2 on PC, storing a full library can quickly consume terabytes. Highly compressed ISOs can slash these sizes dramatically. Some games, particularly 2D fighters or older compilations, can be compressed from over a gigabyte down to mere megabytes (with reports of some games fitting under 200 MB). This compression allows you to store dozens of additional games on a single 64 GB SD card for your Steam Deck or Android phone.