Bitcoin Coin Days Destroyed measures how much dormant coin-age was destroyed by spending on a given day. It combines spent BTC size with the time those coins had remained unspent, so it separates old-coin activation from ordinary turnover more cleanly than raw transfer volume does.
A high reading means spent value was large, old, or both. A low reading means activity was carried mainly by younger or recently moved coins. It is most useful with Transfer Volume, Dormancy, Revived Supply, and Liveliness.
The key distinction is weighting. CDD is not a simple volume metric: moderate spent volume from old coins can matter more than larger volume from young coins. That is why it often says more about holder participation than throughput alone.
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