Any cryptocurrency other than Bitcoin. Short for 'alternative coin.'
An altcoin (alternative coin) is any cryptocurrency other than Bitcoin. The term originated in Bitcoin's early days when every new cryptocurrency was seen as an alternative to Bitcoin. Altcoins range from major platforms like Ethereum and Solana to niche tokens and meme coins. They're often categorized by function: smart contract platforms (ETH, SOL), payment networks (XRP, LTC), DeFi tokens (UNI, AAVE), meme coins (DOGE, SHIB), and many others. The 'altcoin season' refers to periods when altcoins outperform Bitcoin, typically occurring after Bitcoin rallies stabilize and capital flows into smaller coins seeking higher returns.
The term 'altcoin' (alternative coin) originally described any cryptocurrency other than Bitcoin, but its meaning has evolved significantly. In practice, many no longer consider Ethereum an altcoin given its dominant position in smart contracts and DeFi. The altcoin landscape spans thousands of tokens across categories: Layer 1 blockchains (Solana, Avalanche), DeFi protocols (Aave, Uniswap), meme coins (Dogecoin, Shiba Inu), infrastructure (Chainlink, The Graph), and many more. Altcoin markets are characterized by higher volatility than Bitcoin, with stronger rallies during bull markets ('altcoin season') and deeper drawdowns during bears. Most altcoins are highly correlated with Bitcoin's price direction but with amplified moves — a 10% Bitcoin rally might produce 20-50% gains in select altcoins, but the reverse applies equally during downturns.
During the 2021 bull run, Solana (an altcoin) surged from $1.50 to over $250, dramatically outperforming Bitcoin's returns and exemplifying how altcoins can deliver outsized gains — and losses.
Altcoin season typically occurs after Bitcoin has established a strong uptrend and begins consolidating. Capital 'rotates' from Bitcoin into altcoins seeking higher returns. The Altcoin Season Index measures this by tracking whether the majority of top altcoins outperform Bitcoin over a 90-day period.