Most of the U.S. spot Bitcoin ETF market is sitting in one place. Coinbase holds roughly 90% of U.S. spot Bitcoin ETF assets. It serves 8 of the 11 approved ETFs, including BlackRock’s massive IBIT fund. One company. Billions of dollars. You do the math.
The concentration numbers are uncomfortable. A single custodian controls around 81% of all ETF bitcoin assets. Four custodians total split the work across 11 funds, but the weight is almost entirely on Coinbase’s shoulders.
Anchorage Digital serves as a secondary custodian for IBIT, and it holds the rare distinction of being the only federally chartered digital asset bank. That’s basically it for meaningful competition right now.
Traditional banks are mostly on the sidelines. The SEC’s SAB 121 rule forces banks to place digital assets directly on their balance sheets, which is expensive and awkward. Banks have historically kept custody assets off-balance sheet, so the accounting math just doesn’t work for them.
The Federal Reserve chair has actually acknowledged this friction. So until that changes, non-bank custodians like Coinbase dominate by default. Great system.
Here’s where it gets genuinely concerning. A single operational failure at Coinbase could jeopardize over $100 billion in ETF funds. A cyberattack, a sudden outage, or even a legal freeze could delay redemptions and throw ETF rebalancing into chaos.
Multiple funds get disrupted simultaneously. Institutional holdings take a hit. Markets feel it. The irony isn’t lost on anyone that Bitcoin, designed to be decentralized, is now heavily dependent on one custodian’s infrastructure.
There are safeguards in place. Cold storage, multi-party key approvals, SOC audits, NYDFS compliance, segregated bankruptcy-remote accounts, and private insurance all offer some protection. These aren’t nothing. Custodians also rely on hardware security modules to create secure, isolated environments for private key storage, adding another technical barrier against unauthorized access.
But more ETF inflows keep making the concentration problem bigger. Regulators are watching, and potential SEC or CFTC reforms could push for more custodian competition. Rehypothecation practices at custodians could further amplify systemic risks if a crisis were to unfold across multiple funds simultaneously. A bipartisan Congressional resolution introduced by Rep. Flood and Sen. Lummis is actively pushing to end SAB 121 and bring banks into the custody picture.
Basel-style exposure caps have been floated. More banks entering the space could eventually dilute Coinbase’s dominance. That future isn’t here yet though.
