Bitcoin spot ETFs post their best month of 2026 in August, then flip to September outflows

U.S.-listed spot Bitcoin ETFs turned in their strongest month of 2026 in August, helped by a 25% jump in Bitcoin. The tone shifted quickly at the start of September, with flows swinging back into the red. Spot Bitcoin ETFs pulled in $3.52 billion of net inflows in August, a sharp step up from $172 million in July. It marked their best monthly intake since October 2025. Over the same period, Bitcoin rose about 25%, its strongest monthly gain since November 2024. The August surge in demand helped repair much of the ETFs' 2026 shortfall. Year-to-date net outflows narrowed to about $1.77 billion at the end of August from roughly $5.29 billion at the end of July. Investors added money on 16 of 21 trading days in August, including a nine-session streak from Aug. 17 through Aug. 27. Assets under management climbed even faster. Total net assets rose about 31% to $99.61 billion by the end of August from $76.29 billion at the end of July, putting the $100 billion mark within reach. Monthly trading volume increased about 49% to $58.63 billion. Because ETF assets grew faster than Bitcoin's roughly 25% price advance, the expansion appears to reflect meaningful new capital, not just a valuation lift from higher BTC prices. Early September brought a reversal. U.S. spot Bitcoin ETFs posted $236.46 million of net outflows on Sept. 1, wiping out the prior session's $216.70 million inflow. It was the largest one-day withdrawal since July 31. BlackRock's iShares Bitcoin Trust (IBIT) drove most of the selling, shedding $201.18 million, about 85% of the day's total. Fidelity's FBTC saw another $43.67 million leave, while Bitwise's BITB added $8.38 million. Other crypto ETF segments held up better: spot Ethereum ETFs took in about $11 million on Tuesday, and XRP ETFs logged approximately $14.4 million of inflows.