US spot Bitcoin ETFs recorded $986.9 million in net inflows for the week ending September 5, capping a three-week streak that has funneled $3.8 billion into these products. Since regulators approved these funds in January 2024, they have become one of the main conduits for institutional and retail exposure to Bitcoin without holding the asset directly, which is why their weekly flow figures are closely watched as a gauge of demand. The start of 2026 was difficult for Bitcoin ETF flows, and year-to-date net figures remain at roughly negative $1 billion. Three consecutive weeks of heavy buying have not erased that deficit, but they have significantly narrowed it.

Thursday was the main event

Daily inflows during the week were far from evenly distributed. Thursday alone accounted for roughly $731 million in net new capital, the largest single-day haul since January 14. Friday cooled off to $174.6 million, with BlackRock's iShares Bitcoin Trust (IBIT) responsible for $117.4 million of that total and Fidelity's Wise Origin Bitcoin Fund (FBTC) contributing $57.2 million. IBIT has consistently ranked as the largest spot Bitcoin ETF by assets since launch, and its share of weekly flows is often treated as a proxy for where the bulk of ETF demand is concentrated.

Total assets under management across all US spot Bitcoin ETFs stood at $101.3 billion as of the latest data, after briefly touching $103.3 billion during the week. Since their collective launch in January 2024, the funds have accumulated $55.6 billion in cumulative net inflows.

Bitcoin holds steady while altcoin ETFs bleed

Bitcoin's price hovered near $80K during the week, dipping briefly below $79K before recovering to roughly $79,700. Spot Ether ETF inflows dropped 74% week-over-week, while XRP ETF products saw an 83% decline. The divergence suggests that in weeks when risk appetite softens, capital tends to retreat more sharply from newer, smaller altcoin products than from the larger and more liquid Bitcoin funds.

August 2026 delivered $3.5 billion in total Bitcoin ETF inflows, the strongest month since September 2025.

Digging out of a hole

The fact that the year-to-date figure still sits around negative $1 billion, even after $3.8 billion in three-week inflows, illustrates how severe the earlier exodus was. Whether the streak extends into the coming weeks will determine whether 2026 flows turn positive for the first time, a milestone that would require roughly another $1 billion in net inflows.

The $101.3 billion in combined AUM across all spot Bitcoin ETFs represents a significant share of Bitcoin's total market capitalization. At current prices near $80K, Bitcoin's fully diluted market cap sits in the neighborhood of $1.6 trillion, meaning these ETFs collectively hold roughly 6% of all Bitcoin that will ever exist. That share matters beyond the ETF market itself: sustained inflows or outflows from funds holding such a large slice of supply translate into meaningful shifts in Bitcoin demand and available float.