Spot Bitcoin ETFs in the US saw massive net outflows of $450 million on September 15, a sharp reversal that has completely erased the previous momentum that had been building in the market.

This capital exodus unfolded just as the Federal Reserve kicked off its two-day policy meeting, shattering what had appeared to be a brief resurgence in demand. As of this writing, Bitcoin is trading around $75,900, a price point that has now slipped to the lower boundary of the range defined in Glassnode's latest weekly report.

It is worth noting that ETF net flow data only reflects changes in new positions and redemptions at the fund level. It does not include direct information about investor identity or the selling of underlying Bitcoin. However, the data indicates that this shift at the ETF level is closely tied to the intensifying selling pressure across the broader market.

Examining the microstructure of the spot market reveals an even clearer picture of worsening capital flows. The $450 million net outflow on September 15 not only fully reversed the prior day's $159 million net inflow, but it also pushed the cumulative net outflow over the six trading sessions since September 8 to a staggering $753 million.

Data compiled by Woofun AI shows that in Glassnode's 38th week report, the spot cumulative volume delta, which measures the difference between aggressive buying and selling activity, recorded a reading of negative $142 million. This figure has now broken below the negative $115 million lower bound of the statistical range.

This suggests that sellers have established absolute dominance on the centralized trading platforms tracked by Glassnode, and the selling pressure in the spot market continues to accumulate.

Deep data from the derivatives market further confirms the heightened activity on the sell side. The cumulative volume delta in the perpetual contracts market has fallen sharply to negative $605 million, far below its negative $233 million lower threshold, reflecting a strong willingness to sell.

Despite this enormous pressure, market leverage remains at elevated levels. Open interest in futures has dipped slightly from $37 billion to $36 billion, but it still sits above the $36 billion upper alert line. At the same time, funding rates for long positions, which track capital flows between longs and shorts, have risen to $1.4 million and remain within the normal statistical range.

Farside's reporting on September 15 also corroborates the ETF dynamics. However, the current data does not clarify a direct causal link between ETF redemptions and outright selling on exchanges. It merely confirms the prevailing selling pressure across the entire market.

The current state of the market is more appropriately described as 'fragile' rather than 'collapsing.' Bitcoin is facing its first true test ahead of the Fed's policy decision. An ideal stabilization signal would involve prices holding steady, improved spot capital flows, and open interest remaining at reasonable levels.

However, if spot selling pressure intensifies once again, accompanied by further reductions in open interest and sharp fluctuations in funding rates, it could trigger a forced deleveraging event. With ETF holders continuing to sell, Monday's rally has been completely wiped out. Selling pressure in the spot market persists ahead of the policy announcement, significantly amplifying the risk of market volatility.