Crypto's Shifting Balance: Altcoins Put Bitcoin's Supremacy to the Test

The Altcoin Season Index (ASI), which measures how well the top 100 altcoins are performing in comparison to

, has recently arrived at a pivotal point, hinting at possible changes in the market landscape. By the end of September 2025, CoinMarketCap data showed the ASI at 67%, just shy of the 75% mark that historically signals the onset of a full-fledged altcoin season. This is the highest reading since early 2025, highlighting increasing momentum for altcoins as the broader crypto market rebounds.

This upward movement stands in stark contrast to earlier in 2025, when the index often remained below 50%. Experts attribute this change to Bitcoin stabilizing after previous gains, leading capital to flow into alternative coins. Bitcoin’s market share (BTC.D) has slipped from approximately 65% in mid-2025 to about 58–60% by August, pointing to the initial stages of capital rotation into

, , and other major altcoins, though yet indicating a full-scale move into altcoins.

The primary factors shaping current market trends include macroeconomic influences and innovation driven by new narratives. Institutional investment through ETFs and a looser monetary environment have unlocked more liquidity, fueling speculative trading in altcoins. Additionally, the growing appeal of blockchain projects focused on artificial intelligence, decentralized finance (DeFi), and gaming tokens has driven growth in these sectors. Ethereum, for example, has stayed strong in the $4,200–$4,600 range, reinforcing its status as a key player in the ongoing altcoin rotation.

Although the ASI has yet to break into full altcoin season territory, several indicators point to a period of transition. More than 67% of the top 100 altcoins outpaced Bitcoin over the 90 days leading up to September 2025. This includes significant surges for Solana (SOL),

(ADA), and , all of which have experienced double-digit returns recently. Many smaller altcoins tied to AI and gaming have also posted sizeable gains, though price swings in these assets remain pronounced.

Traders are watching both the ASI and Bitcoin dominance closely for further clues. If the Altcoin Season Index rises above 75%, it would mark the start of a traditional altcoin season, often accompanied by powerful rallies in both altcoins and

tokens. On the other hand, should Bitcoin dominance rebound past 60%, it might signal a shift back to Bitcoin-led market momentum.

Currently, the market is in a complex phase of the crypto cycle. While Bitcoin holds a leading position, the ASI’s progress suggests investors are becoming more willing to take risks with altcoins. A gradual strategy is recommended, starting with shifting allocations from Bitcoin to Ethereum and large-cap alternatives early in the altcoin season, then considering smaller-cap coins as the trend matures. Even so, the high volatility and regulatory challenges inherent to altcoins mean that prudent risk management remains essential, especially for speculative bets.