Dark data is the untouched information stored in your systems—up to 55% of all...

https://juliet-wiki.win/index.php/Why_Is_Our_Backup_Taking_Longer_Every_Month%3F_Unpacking_the_Impact_of_Data_Sprawl_and_Dark_Data

Dark data is the untouched information stored in your systems—up to 55% of all data goes unused. This matters because it racks up costs and creates risk, especially when AI sifts through cluttered files