Candidate Block

A candidate block is a proposed block that a miner constructs and attempts to add to the blockchain. It contains a set of transactions selected from the memory pool (mempool), a reference to the previous block, and other metadata like the nonce and timestamp. While it’s not yet confirmed, this block becomes a candidate for validation through the consensus mechanism—typically Proof of Work in networks like Bitcoin.

How Candidate Blocks Are Created

Miners gather unconfirmed transactions from the mempool and organize them into a block that adheres to the network’s rules. The block must also include a reward transaction, often called the coinbase transaction, which pays the miner. The miner then begins hashing this candidate block with different nonces to find a valid hash below the network’s target difficulty.

From Candidate to Confirmed

Once a miner finds a valid hash, the candidate block is broadcast to the network for verification. If accepted by the majority of nodes, it becomes part of the blockchain, and the miner receives the block reward. If another miner wins the race first, the candidate block becomes stale and is discarded.

Its Role in the Mining Process

Candidate blocks are essential in the block creation process. They represent the transitional phase between raw transaction data and a confirmed block. Even though many candidate blocks never make it into the chain, they reflect the constant competition and decentralization that define blockchain mining.