What are Uncle Blocks in Ethereum?

Ethereum is a proof of work-dependent network. Special nodes called miners are tasked with confirming transactions and securing the protocol. They receive rewards whenever they confirm and add a block to the primary chain.

Since mining is competitive, there is an instance where one or more blocks are confirmed at almost the same time.

This clash leads to uncle blocks—NOT orphan blocks.

True, they are part of the network, and the miner receives a lower reward for their effort, but the block isn't part of the longer chain. However, they can be linked to the genesis block. Uncle block rewards significantly diminish, reducing to zero after seven blocks. Uncle blocks aren't part of the canonical truth at that particular chain height.

Uncle blocks can be described as stale blocks that directly contribute to the security of the base chain—in this case Ethereum. As such, they are linked to the primary chain but are not part of the original selection.

Uncle blocks are common in Ethereum because of the shorter block generation time of around 14 seconds.