What Is Block Time?

Block time measures the time it takes the miners or validators within a network to verify transactions within one block and produce a new block in that blockchain.

Blockchains were first popularized by Bitcoin when it was introduced in 2009. The technology has grown as more cryptocurrencies are created, each of which can use a different or identical blockchain, validation methods, and techniques for creating new blocks.

Understanding Block Time

A blockchain is a distributed database that records all transactions within a cryptocurrency network. You can think of a block within the database as a cell in a spreadsheet where transaction information is stored. Bitcoin miners verify the transactions, which takes time because finding the solution to the encryption problem requires the computers to make a vast number of trial-and-error attempts.

On the Bitcoin blockchain, this is called hashing—generating random hexadecimal numbers to try and find one that is less than or equal to one set by the network. When the block solution is found or otherwise validated, a new block is opened. The amount of time it takes to find the solution and create a new block is the block time.

Here are a few key points to remember if you're trying to understand block time:

• A block is a record of the most recent cryptocurrency transactions, similar to a cell in a table of columns and rows.
• Each block contains the information from the block that preceded it in hashed form (that's why it is theoretically impossible to alter cryptocurrency).
• On the Bitcoin blockchain, cryptocurrency "miners" race against each other to generate a random hash plus the nonce that is less than or equal to the target hash. The winner receives a reward.
• Ethereum validators use a different consensus mechanism, which makes the block times shorter.
• Blockchains that use other mechanisms may have shorter or longer block times.

Why Block Times Differ

Consensus mechanisms are what allow a network of participants to agree that a transaction is valid. Cryptocurrencies can use different consensus mechanisms, which, among other factors, affect the time it takes to verify transactions and create new blocks.

Proof-of-work and proof-of-stake are two types of consensus mechanisms that use different transaction verification methods. Each blockchain has a different block time because of the way their mechanisms work—Bitcoin averages about 10 minutes, while Ethereum only takes around 12 seconds.

The exact amount of time it takes for block generation on the Bitcoin proof-of-work blockchain is governed by the difficulty level, which changes with network traffic and the number of miners on the network to keep block times at 10 minutes.

Ethereum uses proof-of-stake, which is much faster because there is no competition for a reward—participants with staked ether are randomly selected to validate the transactions and receive network fees.

Block Time vs. Confirmation Time

Sometimes confused with each other, block times and confirmation times are two different measurements on a blockchain. Confirmation time is the amount of time it takes a blockchain to confirm a transaction.

A block may be opened every 10 minutes on the Bitcoin blockchain, but not all transactions that occur within that period can be sent to the current block to be mined and confirmed. Confirmation can take up to several hours on the Bitcoin blockchain because transactions are sent to a mempool, where they are queued in order of the amount of fees paid.

Users who want their transactions placed in front of others pay more than the average, while those who pay average or below-average fees must wait their turn to be sent to a block, verified, and confirmed at least once.

The Bottom Line

Blocks are one of the structures used in a blockchain that store information. The time it takes to open a new block on a chain is that chain's block time. Block times differ from confirmation times, which can take several hours or days to complete.