Stale Block

Stale block is a block that may be technically valid but is not part of the currently selected chain. In Proof-of-Work systems, this can occur when two miners find valid blocks at nearly the same time.

Some nodes may initially receive one block while others receive the competing block. As additional blocks are found, the network consensus rules determine which branch becomes the accepted continuation.

Mining implications

For a miner, a stale block means that the discovered block did not become part of the current main chain. Depending on the protocol and reward mechanism, the associated block reward may therefore not be realized.

Stale-block frequency can be affected by network propagation time, topology, block production rate, and implementation details.