Definition. A breakdown of the Bitcoin supply by its exposure to potential attacks by quantum computers. Supply is exposed when the public key that controls it is already visible on-chain, either because the output type reveals it or because the holding address has spent before and thereby revealed it. The categories are:

• Taproot: Supply in P2TR outputs.
• P2PK (Satoshi): Supply in P2PK outputs attributed to Satoshi Nakamoto.
• P2PK (Other): All other supply in P2PK outputs.
• Address Reuse (Exchanges): Supply on exchange addresses that have already spent an output.
• Address Reuse (Other): Supply on all other addresses that have already spent an output.
• Not Exposed: All remaining supply.

Technical. The categories are mutually exclusive, assigned in the order listed, and add up to the total supply. Each data point reflects the supply at the end of the month. The metric is refreshed only once per month. Exchange and Satoshi holdings are identified with Glassnode's entity clustering, so the history can revise when the clustering is updated. One series per category.