US spot Bitcoin ETFs shed $450M over three sessions as September selling picks up

US spot Bitcoin ETFs recorded about $450 million of net outflows over three trading sessions from September 8–10, ending one of the strongest recent inflow runs. Redemptions intensified through the week, led by September 10, when withdrawals reached $282.6 million. The pullback followed a sharp contrast with the prior week. For the week ending September 4, spot Bitcoin ETFs attracted roughly $987 million, including a $730.9 million single-day surge on September 3. Within a handful of sessions, nearly half of that momentum faded. Flow data show a clear acceleration in selling pressure. Net outflows were $46.6 million on September 8, widened to $120.2 million on September 9, then spiked to $282.6 million on September 10, the largest single-day outflow in the three-day stretch. ARKB, the ARK 21Shares Bitcoin ETF, accounted for the largest share of the damage. It posted $164.3 million of outflows on September 10 alone, the biggest contributor to that day's redemptions. Most funds saw assets leave during the period, while Morgan Stanley's MSBT was the only product to register modest net inflows. Bitcoin prices tracked the risk-off tone. The cryptocurrency traded near or below $80,000 during the selloff, slipping closer to $77,000 as redemption pressure built. Since the products launched in January 2024, cumulative net inflows total about $55.17 billion. Assets under management across spot Bitcoin ETFs stand near $97.5 billion, roughly 6.28% of Bitcoin's market capitalization. Even with that longer-term build, 2026 has been more challenging. Year-to-date net outflows are around $1.07 billion, leaving overall flows negative since January. The prior three weeks had brought roughly $3.8 billion of net inflows, and the latest selling wave represented only a portion of that total, but the speed of the reversal drew attention: a swing from nearly $1 billion in weekly inflows to $450 million in weekly outflows within a single calendar week. ARKB's outsized role is notable given ARK Invest's appeal to growth-focused, risk-tolerant investors. The heavy concentration of selling on September 10, rather than a more even pace across the three sessions, points to a tipping-point move rather than a gradual reassessment.