I was reading a passage on the bitcoin wiki that pointed out that it doesn't make sense to call invalid chains "orphans," since, by definition, every block in the blockchain except the genesis block has a parent.

Blocks in shorter chains (or invalid chains) are not used for anything. When the bitcoin client switches to another, longer chain, all valid transactions of the blocks inside the shorter chain are re-added to the pool of queued transactions and will be included in another block. The reward for the blocks on the shorter chain will not be present in the longest chain, so they will be practically lost, which is why a network-enforced 100-block maturation time for generations exists.

These blocks on the shorter chains are often called "orphan" blocks. This is because the generation transactions do not have a parent block in the longest chain, so these generation transactions show up as orphan in the listtransactions RPC call. Several pools have misinterpreted these messages and started calling their blocks "orphans". In reality, these blocks have a parent block, and might even have children.

Is there a better way to refer to these blocks?

  • 1
    Perhaps we could call them 'disowned' blocks, since they're no longer the favored child of their parents. /s
    – Nick ODell
    Commented Oct 24, 2014 at 2:33
  • 1
    related: What are orphaned and stale blocks?
    – Murch
    Commented Oct 24, 2014 at 15:18

1 Answer 1


Pieter Wuille suggests extinct blocks:

The first is perhaps best called extinct blocks. These are blocks that were produced by building on an block that is no longer the active tip of the chain. Some nodes may have considered it to be the best block at some point, but they switched to another chain which does not contain the relevant block anymore. They are valid, verified, and their ancestry up to the genesis block is fully known - they're just not currently 'active'. They are sometimes called stale blocks (typically in the context of mining software realizing it built on old data) or orphan blocks. The latter name [orphans] originates from the fact that payouts from extinct blocks are denoted as "orphaned" in the reference client (referring to the fact that their coinbase transactions are now orphaned).

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