What is Bitcoin Dominance?

Bitcoin dominance (BTC.D) is the percentage of total crypto market cap held by Bitcoin. In early 2017 dominance was above 85%; by the 2018 altseason it had dropped to roughly 35%, and since then it has cycled in the 45-65% range. Rising dominance signals risk-off rotation toward Bitcoin; falling dominance often precedes altcoin outperformance. For traders, BTC.D is read alongside price: when dominance breaks down from a range, alts can outperform on a relative basis; when it spikes, alts lose ground in BTC terms even if their USD price is rising. ETH dominance, TOTAL2 (ex-BTC), and TOTAL3 (ex-BTC and ETH) are companion indices used to gauge altcoin breadth. Stablecoin dominance (USDT.D + USDC.D) trending up is a sign of risk-off positioning. As with any single metric, BTC.D should be read alongside macro inputs (DXY, rates) and positioning indicators (open interest, funding) before sizing positions.