Orphan Block

"Orphan block" is older terminology for a valid block that didn't end up in the canonical chain. Modern Bitcoin Core documentation prefers stale block for this concept, reserving "orphan" for the genuinely rare case of a block whose parent the local node hasn't yet received.

In practice, when two miners find a valid block at the same height almost simultaneously, the network temporarily splits. Each half builds on the block it saw first. Within a block or two, one branch typically pulls ahead, and the other branch's tip block is abandoned. The miner of that abandoned block doesn't get paid. The public bitcoin-data/stale-blocks dataset counts between 28 and 93 of these stale blocks a year from 2022 through 2025.

The naming history is messy. You'll see "orphan," "stale," and "uncle" (the Ethereum term) all used interchangeably in older write-ups. For Bitcoin in 2026, the cleaner distinction is:

• Stale block - a valid block, fully verified, that lost the race. The block existed; it just isn't part of the longest chain anymore.
• Orphan block - a block whose parent the local node doesn't have. Usually a propagation artifact, almost always resolved within seconds when the parent arrives.

Both are normal consequences of a globally distributed proof-of-work race. Neither indicates anything wrong with Bitcoin. See Reorg for what happens to the transactions inside a stale block.