What is Bitcoin dominance and how to read its chart

Bitcoin dominance measures BTC’s share of total crypto market capitalization. It is the single most watched macro indicator for timing capital rotation between bitcoin and altcoins. Summary Bitcoin dominance (BTC.D) is the ratio of bitcoin’s market capitalization to the total cryptocurrency market capitalization, expressed as a percentage. BTC.D peaked near 99 percent in 2013, fell to a record low of roughly 38 percent during the 2018 ICO bust, and has cycled in a 33 to 73 percent range since 2017. As of mid-2026, BTC.D sits in the mid to high 50s after retreating from a four-year high above 63 percent reached in mid-2025, driven largely by institutional ETF inflows concentrating in bitcoin. The Altcoin Season Index, which scores how many of the top 100 altcoins outperform bitcoin over 90 days, reads below 40 in August 2026, well short of the 75 threshold that confirms a broad altcoin season. Reading BTC.D in isolation is misleading; the metric must be cross-referenced with total market capitalization and volume to distinguish between four distinct market regimes. Bitcoin dominance is one of those numbers that every crypto trader checks but few use correctly. The metric appears sim...