Dark data is all the info your company stores but never uses—like emails, logs,...

https://www.ready-bookmarks.win/dark-data-is-the-info-companies-collect-but-don-t-use-up-to-55-of-all-data

Dark data is all the info your company stores but never uses—like emails, logs, or old files. Around 55% of data can be dark, which adds up to wasted storage costs and hidden risks