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Candidate Block Meaning

Jan 18, 2024 | Updated Jan 18, 2024
A candidate block is a container for transactions selected from the memory pool. It has the potential to be added to the blockchain or rejected by the network.

What is a Candidate Block?

A block already added to the blockchain is considered a valid/confirmed block. Before that, it was just a candidate block. In blockchain networks, miners and validators try to add verified blocks to the blockchain. Therefore, a candidate block, also known as a “proposed block”, is a temporary block that a network participant proposes to be included in a network. This means that it is not yet valid and the network can either approve or reject it. 

So, how are temporary blocks created? 

Validators or miners first gather and organize multiple unconfirmed transactions from the validating or mining node’s waiting area, known as the mempool (memory pool). A block can only contain a limited number of transactions due to space limitations. The container filled with these unconfirmed transactions is a temporary block. It is “temporary” since it is not yet validated.

Every block is mined or validated based on the network’s consensus mechanism. This ensures that there is integrity and consistency within the blockchain network. The temporary block also prevents double-spending and adds a layer of security as only valid transactions are added to the blockchain. 

How do temporary blocks become confirmed blocks?

To verify transactions in proof-of-work (PoW) networks, such as Bitcoin, miners compete to solve a complex mathematical puzzle using specialized hardware. The winning miner gets the opportunity to add their proposed block to the blockchain and receive mining rewards. 

In proof-of-stake (PoS) blockchains, the network’s algorithm pseudo-randomly selects a validator to create a temporary block. Other validators verify the block’s validity, and with enough approvals, the proposed block becomes a confirmed block.

If a proposed block is successfully validated, the blockchain records it, making it a confirmed block. The rest of the nodes on the network update their version of the blockchain with this new valid block included. The miner or validator is then rewarded with a block reward. However, if the network rejects it, the transactions are returned to the mempool, where they are selected for the next proposed block.Candidate Block


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