US spot bitcoin exchange-traded funds recorded $31.0 million in net inflows on September 28, according to Farside Investors' daily fund-flow table. BlackRock's iShares Bitcoin Trust (IBIT) accounted for $54.8 million of that total, while the remaining funds in the category posted a combined $23.8 million in net outflows.

The single-day figures extend a run of concentration in the largest fund. US spot ether ETFs, tracked separately by Farside, drew $17.1 million in net inflows the same day.

How did the week shape up?

For the trading week of September 21 through September 25, Farside's daily bitcoin rows sum to $2,385.8 million in net inflows across US spot bitcoin funds. IBIT captured $1,157.6 million of that, and Fidelity's Wise Origin Bitcoin Fund (FBTC) took in $701.6 million.

That IBIT weekly figure was not its second-largest since October 2025, as an earlier version of the report stated. Farside's dated rows show larger IBIT weekly totals in the weeks beginning October 6, 2025, at $2,625.3 million, and August 17, 2026, at $1,330.8 million.

BlackRock reported $66.79 billion in IBIT net assets as of September 28, underscoring the scale gap between the fund and the rest of the category.

What do the year-to-date flows show?

Farside's daily totals trace a sharp recovery across 2026. Net flows for the category bottomed at $5,689.6 million in outflows on July 13. By September 28, the year-to-date sum had swung to $1,052.3 million in net inflows — a reversal of roughly $6.74 billion over about two and a half months.

Lifetime cumulative net inflows across the US spot bitcoin ETF category stood at approximately $57.65 billion on Farside's table as of the same date.

Ether funds show a similar direction of travel. Farside's ether rows sum to $689.8 million in net inflows during the September 21–25 week, following $140.6 million in net outflows the week prior.

What are the limits of the data?

Farside's tables record subscriptions and redemptions by fund. They do not identify who the buyers are, whether institutional or retail, and they do not establish that current flow levels will persist. Earlier claims about investor type and liquidity preference tied to these figures have been retracted for lack of support.

The operational takeaway for issuers is straightforward: flows are concentrating in the two largest bitcoin vehicles, IBIT and FBTC, while smaller funds absorb redemptions even on positive aggregate days. That divergence pressures fee revenue and secondary-market liquidity at the tail of the category.

The next test comes with October's full-week flow prints, which will show whether September's recovery holds or whether the July outflow trough marks the start of a more volatile regime for spot crypto ETF demand.