// GLOSSARY -- BLOCKCHAIN & CRYPTO FUNDAMENTALS

What is Block?

1 min read Updated

A block is a batch of validated transactions bundled together and added to the blockchain — containing a header with metadata and a body with transactions, forming one link in the chain.

WHY IT MATTERS

Blocks are the fundamental unit of blockchain data. Instead of processing transactions individually, blockchains batch them for efficiency. Each block contains a reference to the previous block, a timestamp, a Merkle root, and consensus data.

Block parameters vary: Bitcoin ~10 minutes with 1MB limit, Ethereum ~12 seconds, Solana ~400ms. These parameters reflect different priorities — security vs speed vs throughput.

Block production is the core consensus function: validators compete or are selected to produce the next block, ordering transactions within it — which has implications for MEV.

FREQUENTLY ASKED QUESTIONS

What's in a block header?
Previous block hash, Merkle root of transactions, timestamp, validator/nonce info, and gas/difficulty targets. The header gets hashed to create the block's identity.
What determines block size?
Protocol rules. Bitcoin has a weight limit (~4MB), Ethereum uses a gas limit (~30M gas). These cap transactions per block and create the fee market.
Can blocks be empty?
Yes. Validators can produce blocks with zero transactions. This sometimes happens on quiet networks but is rare during normal activity.

FURTHER READING

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