A collection of transaction data that is bundled together and added to the blockchain. Each block contains a timestamp, transaction records, and a reference to the previous block's hash. Blocks are created at regular intervals depending on the blockchain's design.
A block is the fundamental unit of data storage on a blockchain. Each block contains a batch of verified transactions, a timestamp, a reference to the previous block's cryptographic hash, and a nonce (in proof-of-work systems). Blocks are created at regular intervals — approximately every 10 minutes for Bitcoin, every 12 seconds for Ethereum, and sub-second for high-performance chains like Solana.
The size and frequency of blocks directly impact a blockchain's throughput and capacity. Bitcoin blocks are limited to approximately 1 MB (with SegWit extensions), constraining throughput to about 7 transactions per second. Ethereum blocks have a gas limit that determines how many transactions can fit. Block size debates have been among the most contentious in crypto history, with the Bitcoin block size war ultimately leading to the Bitcoin Cash hard fork in 2017.
Block sizes vary by blockchain. Bitcoin blocks are about 1 MB (up to 4 MB with SegWit). Ethereum blocks are limited by gas rather than raw size. Solana blocks can be much larger due to its high-throughput design.
Bitcoin: ~10 minutes. Ethereum: ~12 seconds. Solana: ~400 milliseconds. Different blockchains optimize for different block times based on their design priorities.
When blocks are full, transactions must wait in the mempool. Users can pay higher fees to prioritize their transactions. Full blocks during peak demand cause fee spikes, especially on networks like Ethereum.
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A distributed, immutable ledger technology that records transactions across a network of computers. Each block contains a cryptographic hash of the previous block, creating a chain that cannot be altered retroactively. Blockchains enable trustless, transparent record-keeping without a central authority.
HashA fixed-length string of characters produced by a cryptographic hash function from input data of any size. Hashes are used extensively in blockchain to link blocks, verify data integrity, and secure transactions. Even a tiny change in input produces a completely different hash output.
NonceA number used once in cryptographic communication, particularly in proof-of-work mining where miners must find a nonce that produces a hash meeting the network's difficulty target. The nonce is incremented repeatedly until a valid hash is found. It is a critical component of the mining process.
Gas FeeThe cost required to execute a transaction or smart contract operation on a blockchain like Ethereum. Gas fees compensate validators for the computational resources needed to process transactions. Fees fluctuate based on network congestion and the complexity of the operation.