Bitcoin's Centralization Crisis: Three Reorgs in Four Weeks

A recent Bitcoin blockchain reorg on September 11, 2026, is raising concerns about network centralization. The incident occurred when SpiderPool and AntPool each mined a valid block at height 966,500 within seconds of each other. The chain with more accumulated proof-of-work won, and AntPool's block became canonical. However, SpiderPool's version was discarded along with approximately 3.1389 BTC in block reward, worth around $240,000 at current prices.

This is the third one-block reorg in a four-week span, following similar events on August 16 and August 24. The increasing frequency of these events has led security researchers to point out that the same concentration that makes these races more frequent also lowers the bar for something more deliberate.

According to Hasrate Index, the top two mining pools, Foundry USA and AntPool, control a combined 44.6% of Bitcoin's total network hashrate as of September 18, 2026. This concentration is raising concerns about the network's security model, which assumes that no single actor controls enough hashrate to rewrite history or censor transactions at will.