Crypto glossary
Coin days destroyed
Coin days destroyed (CDD) weights each coin moved by the days it sat idle, so spending by long-dormant holders shows up as large spikes on the chart.
Every unspent coin accumulates coin days: one bitcoin held for 100 days carries 100 coin days. When it moves, those days are 'destroyed'. Summing this across all transactions in a day gives coin days destroyed, a measure that gives far more weight to old coins than to the same amount of fresh coins changing hands.
The metric was proposed on the Bitcoin forum in 2011 and is used to detect when experienced holders wake up. Spikes in CDD during rallies often coincide with long-term holders distributing, while low readings during declines suggest veterans are staying put. Variants such as binary CDD, supply-adjusted CDD and dormancy refine the signal.
A single spike can come from an exchange or custodian reorganising its wallets, from early miner coins being moved for security reasons or from a known entity such as a government shifting seized funds. Analysts therefore check where the coins went before calling it selling.
Example
A wallet dormant since 2011 moves 1,000 BTC, adding more than 5 million coin days destroyed in one day and sparking speculation about an early miner selling.