Bitcoin’s market share fell to about 57 percent in September, according to Binance Research’s Monthly Market Insights and the TradingView BTC Dominance chart, a level that historically lines up with stronger relative performance in non-BTC assets.
The Altcoin Season Index sits near the 75 line that many participants use as confirmation that altcoins are outperforming Bitcoin across the top cohort. The index’s own definition sets that threshold as 75 percent of the top 50 beating BTC over 90 days.
What changed for altcoins after July to September data
Derivatives activity accelerated into late summer. Binance Futures’ monthly volume reached about 2.626 trillion dollars in August 2025, the highest this year based on a dataset published by CryptoQuant.
Liquidity conditions appear supportive too. Stablecoin market capitalization is near record highs, per DefiLlama’s live dashboard and CoinDesk Data’s September report estimating roughly 293 billion dollars.
How the SEC’s new ETF standard could shift flows
Policy can change flows at the margins. On September 17, 2025, the U.S. Securities and Exchange Commission approved generic listing standards for commodity-based exchange-traded products, including spot digital assets. The agency said exchanges may list qualifying products without submitting a separate rule change for each one.
“Today’s generic listing standards afford the same treatment to covered commodity-based ETPs,” Commissioner Hester Peirce said on the day of approval. Easier listings could expand the menu beyond Bitcoin and Ether over time, a development that has, in past cycles, encouraged selective rotations.
What comes next: For confirmation, analysts typically look for Bitcoin dominance to trend lower for multiple weeks alongside the Altcoin Season Index sustaining above 75, plus rising spot and perpetual volumes across several venues, not just one. The data above will be updated by the linked dashboards and monthly reports in early October.
