SBI Crypto, part of Japan’s SBI Group, has shut down its Bitcoin mining pool after five years in operation. On its own, the move marks the exit of a mid-sized pool. In the context of Bitcoin’s current hashpower distribution, it has also revived questions about mining concentration.
The timing stands out because the three largest mining pools now account for roughly 60% of Bitcoin network block production.
SBI Crypto stopped accepting hashpower on July 31
According to a customer notice signed by CEO Hiroaki Morita, SBI Crypto stopped accepting hashpower at 7:00 a.m. Japan time on July 31, which was 22:00 UTC on July 30. Any hashpower submitted after that cutoff would not be included in the final payout calculation.
As of June 30, the pool’s seven-day average hash rate was about 20.9 EH/s, representing roughly 2.2% of the Bitcoin network. By the time of the shutdown, however, its seven-day average hash rate had already dropped about 64% over the previous month. The notice did not give a reason for the closure. It told customers to move their hashpower to Braiins, Luxor Pool, or NeoPool.
Foundry USA, AntPool, and F2Pool hold about 60%
The bigger issue is how much block production is concentrated among the leading pools. Data from Hashrate Index shows that Foundry USA, AntPool, and F2Pool have recently accounted for about 60% of Bitcoin blocks, and their combined share reached around 64.8% in the week of July 20.
Add ViaBTC and the top four pools come close to 70% of the network’s hashpower share. The exit of a mid-sized pool such as SBI can push more hashpower that had been spread across smaller operators toward these larger pools.
Why concentration is watched closely
Mining concentration is treated as a risk because pools act as coordination points for block production decisions. In theory, if a small number of pools were to control more than half of the network’s hashpower together, they would have the ability to mount a 51% attack or censor specific transactions. That would run against Bitcoin’s core promise of decentralization and trust minimization.
That said, pool concentration does not mean hashpower ownership is held by a single entity. The actual computing power behind a pool comes from large numbers of independent miners, and those miners can redirect their machines to another pool if they disagree with how one operator behaves.
Seen that way, a 60% concentration level is a warning sign worth monitoring, but it points to concentration at the coordination layer rather than proof that hashpower ownership itself has been monopolized by a handful of actors.