Dark data is all the information companies keep but don’t use—like old emails,...

https://www.bokkmarking-signs.win/dark-data-is-the-inactive-or-unused-information-stored-but-not-analyzed-often

Dark data is all the information companies keep but don’t use—like old emails, logs, or files. It often makes up 60-80% of stored data and can cost businesses around $2.5 million each year in wasted storage and missed opportunities