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UncleBlock is a sub-structure of Block. It is the ordered list of uncle blocks.

Structure of UncleBlock

Fields & Description

headerHeaderBlock header of the uncle block. The structure is the same as the header.
proposals[H80]An array of short transaction IDs of the proposed transactions in this uncle block. For more, see proposals

Uncle Block

Uncle blocks are created when 2 blocks are mined and submitted to the ledger at roughly the same time. Only 1 can enter the ledger as an included block, and the other does not.

Uncle Block Condition

Block B1 is considered to be the uncle of block B2 if all the following conditions are met:

  • B1 should not be on the main chain.
  • Both are in the same epoch
    An epoch is a period of time for a set of blocks.
    with identical difficulty.
  • B2 has higher block number/height than B1.
  • B1's parent is either B2's ancestor or an uncle embedded in B2, or any of B2's ancestors.
  • B2 is the first block in its chain to reference B1.