The Crypto Fear & Greed Index is a single number between 0 and 100 that compresses the emotional state of the crypto market into one readable signal. Below 50, the market leans fearful. Above 50, it leans greedy. The closer the score is to either extreme, the more one-sided market sentiment has become — and those extremes are where the index earns its keep.

Two providers dominate: Alternative publishes the most widely cited version, built primarily around Bitcoin signals. CoinMarketCap (CMC) runs its own variant with broader asset coverage. Both draw from the same general family of inputs:

• Volatility — how sharply prices are swinging relative to recent averages
• Market momentum and volume — whether buying pressure is…