How the index is calculated
We take the 50 largest cryptocurrencies that are not Bitcoin, stablecoins or wrapped tokens and count how many did better than Bitcoin over the last 30 days. If 75% or more beat BTC, it is altcoin season; if 25% or fewer did, it is Bitcoin season.
This is a simplified 30-day version of the classic 90-day index, so it reacts faster. The bar chart shows each coin’s performance relative to Bitcoin.