: CHD is a lossless compression format. You get the exact same game, audio, and visuals.

(and its popular fork ), using highly compressed games allows you to store a significantly larger library on your Android device without sacrificing game data or quality. Recommended Compression Formats

Don't download pre-compressed files from sketchy sites; it's safer and more reliable to compress your own ISOs using or chdman . Download chdman : This is part of the MAME tools suite. Run the Command : Use createcd to turn your ISO into a CHD.