Is it Altcoin Season or Bitcoin Season? The index counts how many of the top 100 coins (stablecoins and wrapped/staked tokens excluded) beat Bitcoin over the last 30 days. 75 or above is Altcoin Season; 25 or below is Bitcoin Season.
61 of 81 qualifying coins outperformed Bitcoin's +7.78% move over the last 30 days. Basis: 30 days (CoinGecko free tier); CoinMarketCap uses 90 days, so readings differ.
A 0 to 100 score showing what share of the largest 100 cryptocurrencies outperformed Bitcoin over a recent window. When most alts beat BTC the market is in "altcoin season"; when Bitcoin leads it is "Bitcoin season". Stablecoins and wrapped or staked derivatives (WBTC, stETH, USDT…) are excluded because they track another asset.
Take the top 100 coins by market cap, drop stablecoins and wrapped tokens, count how many have a higher 30-day return than Bitcoin, and express that as a percentage. 75%+ = Altcoin Season, 25% or less = Bitcoin Season. We recompute it every time the market feed runs.
Mostly for rotation context. A rising index means risk appetite is broadening beyond Bitcoin; a falling one means capital is concentrating in BTC (often risk-off). It pairs well with Bitcoin dominance, which measures the same rotation by market cap rather than by breadth.
