Antpool and Foundry USA both mined Bitcoin block 941,881 within 12 seconds of each other on March 24, 2026, creating a rare two-block reorganization event. Foundry won the race by extending its chain with six consecutive blocks (941,883 through 941,886), causing Antpool's and ViaBTC's blocks to be orphaned. The event occurred because Bitcoin blocks must propagate across a global network before all nodes agree on the chain tip, and when two miners find valid blocks before learning about each other's discovery, the network temporarily splits until one chain accumulates more proof-of-work.
Bitcoin Mining Races Occur When Network Propagation Creates Simultaneous Valid Blocks
A new Bitcoin block must physically propagate from node to node across a global network before every participant agrees on the current chain tip. That trip takes seconds, sometimes longer on a congested connection. If a second miner finds a valid block before the first block has finished spreading to them, they build on the version they last saw and broadcast their own competing block. For a brief window, two equally valid blocks exist at the same height, each with its own set of confirmed transactions. Neither block violates protocol rules; the only difference is timing and which nodes heard about which one first. Roughly half the network ends up mining on top of one candidate, the rest on the other.
Proof-of-Work Accumulation Resolves Competing Chains
Bitcoin resolves simultaneous blocks by having whichever chain accumulates more proof-of-work become the one every node switches to, and the other side's block or blocks get discarded. Discarded blocks, called "orphaned" or "stale," stop being part of the chain everyone recognizes, and any transactions inside them that weren't also confirmed on the winning side drop back into the mempool to be picked up again in a future block. Most of the time, this resolves after just one extra block. A genuine two-block-deep race is rare because it requires the coin-flip odds to land the same way twice in a row.
Foundry Extended Its Chain Six Blocks After March 24 Split
After Antpool and Foundry USA each produced their own version of block 941,881 twelve seconds apart on March 24, 2026, ViaBTC extended Antpool's version with block 941,882 while Foundry extended its own version. For one block, the network was split between two valid chains. Then Foundry pulled ahead, mining blocks 941,883 through 941,886 in succession (six consecutive blocks on its branch). Every node reorganized to Foundry's version, and the blocks Antpool and ViaBTC had mined were orphaned; their miners lost the block reward and fees for that work, though the transactions themselves rejoined the mempool and were confirmed again shortly after.
Bitcoin analyst b10c, who first flagged the event publicly, called it "a rare-ish two block fork/reorg between Foundry and AntPool+ViaBTC." Coverage of the event noted that shrinking margins have been pushing smaller miners out and concentrating hashpower into fewer, larger pools.
Block Timestamp Data Shows 9.2% of Intervals Under 60 Seconds
Data shows 7.3% of blocks over a recent 3-day span landed within 60 seconds of the one before. Pulling real block timestamps directly from mempool.space for the three days before the reorg (heights 941,452 to 941,887), 40 of 435 consecutive-block intervals (about 9.2%) landed within 60 seconds of each other, including one pair just 5 seconds apart. Every one of those close calls is a moment where a genuine race condition existed on the network. Almost all of them resolve within that same single block, silently, because the next miner to find a block overwhelmingly just builds on whichever tip reached them first.
Compact block relay and dedicated low-latency relay networks like FIBRE, which most large pools now use, have made the propagation delays that cause races shorter than they were in Bitcoin's earlier years.
FAQ
What happened when Antpool and Foundry mined block 941,881 on March 24, 2026?
Antpool and Foundry USA both mined block 941,881 within 12 seconds of each other on March 24, 2026. ViaBTC extended Antpool's version with block 941,882 while Foundry extended its own version. Foundry then mined blocks 941,883 through 941,886 in succession, causing every node to reorganize to Foundry's version and orphaning Antpool's and ViaBTC's blocks.
How does Bitcoin resolve competing blocks at the same height?
Bitcoin resolves competing blocks by having whichever chain accumulates more proof-of-work become the one every node switches to. The other side's blocks get discarded and are called "orphaned" or "stale." Transactions inside orphaned blocks that weren't also confirmed on the winning side drop back into the mempool to be picked up again in a future block.
How often do Bitcoin blocks land within 60 seconds of each other?
Data from mempool.space for heights 941,452 to 941,887 shows 40 of 435 consecutive-block intervals (about 9.2%) landed within 60 seconds of each other, including one pair just 5 seconds apart. Data shows 7.3% of blocks over a recent 3-day span landed within 60 seconds of the one before.
