Altcoin spot volume nears 4x Bitcoin’s as ETF inflows shrink across five sessions

Altcoin spot volume has climbed to nearly four times Bitcoin's, the highest ratio since September 2025, according to Glassnode.

Wintermute says retail clients on its OTC desk sold BTC last week to fund that rotation, while US spot Bitcoin ETFs took in nearly $2.4 billion over the same five sessions. Each day's ETF inflow came in below the previous day's, dropping from $999 million on Sept. 21 to $134.5 million on Sept. 25.

Bitcoin is the funding asset

Wintermute's Sept. 28 OTC report described net BTC selling on its desk, driven mainly by retail clients taking profits and moving into altcoins.

Glassnode's data shows how wide the move outward has become, with 72.5% of the altcoins it tracks outperforming Bitcoin through Sept. 23, up from 39% during August's squeeze.

Altcoin perpetual open interest barely expanded over the prior 30 days, and fewer than half of tracked markets added positions, leading Glassnode to describe that stage of the rally as mostly spot-driven.

Glassnode added that similar bursts of aggressive risk-taking have often coincided with local Bitcoin tops, and it treats the ratio as a historical warning condition.

Wintermute noted that breadth has stretched to a level where the weeks that came next were flat to negative in more than 80% of comparable cases, with early-cycle periods as the exception. Wintermute wants Bitcoin to push higher to recycle fresh wealth into the alt cycle.