What Happens When Two Miners Find a Block at the Same Second? Inside an Orphan Race

Why Two Miners Can ‘Win’ astatine Once

Bitcoin mining is simply a contention with nary referee watching the decorativeness enactment successful existent time. A caller artifact has to physically propagate (i.e. hop from node to node) crossed a planetary web earlier each subordinate agrees connected what the existent extremity of the concatenation is. That travel takes seconds, sometimes longer connected a congested connection.

If a 2nd miner finds a valid artifact of their ain earlier the archetypal artifact has finished spreading to them, they physique connected the mentation they past saw (usually the erstwhile block) and broadcast their ain competing block. For a little window, 2 arsenic valid blocks beryllium astatine the aforesaid height, each with its ain acceptable of confirmed transactions and its ain proposition for what happens next.

Neither artifact is “wrong” arsenic some fulfill each regularisation of the protocol; the lone happening separating them is timing and which nodes happened to perceive astir which 1 first. Roughly fractional the web ends up mining connected apical of 1 candidate, the remainder connected the other, and Bitcoin concisely has 2 honest, simultaneous versions of itself.

How the Tie Actually Gets Broken

Bitcoin doesn’t resoluteness this by vote, authority, oregon whoever technically recovered their artifact first. It resolves it the aforesaid mode it resolves everything, i.e. whichever concatenation accumulates much proof-of-work becomes the 1 each node switches to, and the different side’s artifact oregon blocks get discarded.

Discarded doesn’t mean destroyed past was rewritten, but it means that that block, called “orphaned” oregon “stale,” stops being portion of the concatenation everyone recognizes, and immoderate transactions wrong it that weren’t besides confirmed connected the winning broadside simply driblet backmost into the mempool to beryllium picked up again successful a aboriginal block.

Most of the time, this resolves aft conscionable 1 other block, and cipher extracurricular mining-infrastructure circles notices. A genuine two-block-deep contention (where the necktie someway survives an full further circular without 1 broadside pulling ahead) is rare capable to marque headlines erstwhile it happens, precisely due to the fact that it requires the coin-flip likelihood to onshore the aforesaid mode doubly successful a row.

The March 2026 Case: When the Coin Flip Repeated

That’s precisely what happened connected March 24, 2026. After Antpool and Foundry USA each produced their ain mentation of artifact 941,881 12 seconds apart, ViaBTC extended AntPool’s mentation with artifact 941,882 portion Foundry, moving disconnected its ain tip, extended its mentation too. For 1 block, the web was genuinely divided down the mediate betwixt 2 valid chains. Then Foundry pulled ahead, mining blocks 941,883 done 941,886 successful succession (six consecutive blocks connected its branch) until its concatenation was, successful the words of 1 Bitcoin developer tracking the event, “the heaviest by a wide margin.”

Every node reorganized to Foundry’s version, and the blocks AntPool and ViaBTC had mined were orphaned; their miners mislaid the artifact reward and fees for that work, though the transactions themselves rejoined the mempool and were confirmed again soon after.

Reorganization Diagram erstwhile 2 blocks are mined astatine the aforesaid time.

Bitcoin expert b10c, who archetypal flagged the lawsuit publicly, called it “a rare-ish 2 artifact fork/reorg betwixt Foundry and AntPool+ViaBTC.” Rare is right, but the lawsuit besides drew attraction to a little comfy trend, i.e. Foundry stringing unneurotic six blocks successful a enactment is easier for a excavation that already commands a ample stock of web hashrate, and sum of the lawsuit noted that shrinking margins person been pushing smaller miners retired and concentrating hashpower into fewer, larger pools.

A much concentrated web doesn’t marque a single-block contention much common, but it does marque a well-resourced pool’s likelihood of winning immoderate fixed contention (and stringing unneurotic the follow-up blocks that extremity one) measurably amended than a tiny miner’s.

Hashrate controllers, superior entities, logged July 16, 2026.

The Everyday Version Is Boring, and That’s the Point

Two-block reorgs are the exception; the underlying contention information down them is not. Pulling existent artifact timestamps straight from mempool.space for the 3 days earlier the reorg (heights 941,452 to 941,887), 40 of 435 consecutive-block intervals (about 9.2%) landed wrong 60 seconds of each other, including 1 brace conscionable 5 seconds apart. Every 1 of those adjacent calls is simply a infinitesimal wherever a genuine contention condition, nevertheless brief, existed connected the network.

Almost each of them resoluteness wrong that aforesaid azygous block, silently, due to the fact that the adjacent miner to find a artifact overwhelmingly conscionable builds connected whichever extremity reached them first, and the likelihood of 2 ties successful a enactment are long. Compact artifact relay and dedicated low-latency relay networks similar FIBRE, which astir ample pools present use, person made the propagation delays that origin races shorter than they were successful Bitcoin’s earlier years (which is precisely wherefore a contention that survives 2 afloat blocks, similar AntPool and Foundry’s did, is uncommon capable to beryllium newsworthy alternatively than routine).