A set of entries produced by a leader during a single slot. A block contains transactions bundled into entries, each with a PoH hash proving ordering. Blocks are broken into shreds for network propagation via Turbine. Maximum block size is limited by compute units (48M CU cap per block) rather than byte size.
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A set of entries produced by a leader during a single slot. A block contains transactions bundled into entries, each with a PoH hash proving ordering. Blocks are broken into shreds for network propagation via Turbine. Maximum block size is limited by compute units (48M CU cap per block) rather than byte size.
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Think of it as part of the chain machinery that keeps ordering, execution, or consensus moving.
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Consensus, leader rotation, slots, epochs, and the runtime.
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Block (block) Category: Core Protocol Definition: A set of entries produced by a leader during a single slot. A block contains transactions bundled into entries, each with a PoH hash proving ordering. Blocks are broken into shreds for network propagation via Turbine. Maximum block size is limited by compute units (48M CU cap per block) rather than byte size. Related: Slot, Shred, Entry
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A time window during which a designated leader validator can produce a block. Each slot lasts approximately 400 milliseconds. Slots are numbered sequentially from genesis and grouped into epochs of 432,000 slots (~2-3 days). Not every slot produces a block—a skipped slot means the leader was offline or too slow.
The smallest unit of block data propagated through the network via Turbine. Blocks are split into shreds of up to 1,228 bytes each (fitting in a single UDP packet). Shreds are Reed-Solomon erasure coded—typically 32 data shreds produce 32 recovery shreds—so blocks can be reconstructed even if up to half the shreds are lost.
An ordered unit within a block containing a mix of PoH ticks and transaction batches. Each entry includes a PoH hash, a count of hashes since the previous entry, and zero or more transactions. Entries without transactions are tick entries that advance the PoH clock; entries with transactions prove those transactions occurred between two points in time.
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The number of blocks produced in the ledger since the genesis block. Block height increments only for slots that successfully produce a block (skipped slots do not increment it), so block height is always less than or equal to the current slot number. Block height is accessible via the getBlockHeight RPC method and the Clock sysvar.
The process of distributing a newly produced block from the leader to all validators in the cluster. Solana uses Turbine for fast propagation—the leader shreds the block, erasure-codes the shreds, and feeds them into the Turbine tree. Target propagation latency is under 200ms for the full cluster.
A RocksDB-based database that stores raw shreds and block metadata on the validator's disk. Blockstore indexes shreds by slot and shred index, enabling block reconstruction and historical queries. It is separate from AccountsDB—Blockstore holds the ledger history while AccountsDB holds the current state.
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A time window during which a designated leader validator can produce a block. Each slot lasts approximately 400 milliseconds. Slots are numbered sequentially from genesis and grouped into epochs of 432,000 slots (~2-3 days). Not every slot produces a block—a skipped slot means the leader was offline or too slow.
The smallest unit of block data propagated through the network via Turbine. Blocks are split into shreds of up to 1,228 bytes each (fitting in a single UDP packet). Shreds are Reed-Solomon erasure coded—typically 32 data shreds produce 32 recovery shreds—so blocks can be reconstructed even if up to half the shreds are lost.
An ordered unit within a block containing a mix of PoH ticks and transaction batches. Each entry includes a PoH hash, a count of hashes since the previous entry, and zero or more transactions. Entries without transactions are tick entries that advance the PoH clock; entries with transactions prove those transactions occurred between two points in time.
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A clock mechanism that cryptographically proves the passage of time between events. PoH uses a sequential SHA-256 hash chain where each output becomes the next input, creating a verifiable ordering of events without requiring consensus. The leader produces ~400,000 hashes per slot (~400ms), and any validator can verify the sequence in parallel, enabling Solana's high throughput by removing the need for validators to agree on time.
Solana's custom BFT consensus algorithm built on top of Proof of History. Tower BFT uses PoH as a clock to reduce communication overhead in traditional PBFT from O(n²) to O(n). Validators vote on forks with exponentially increasing lockout periods—each consecutive vote doubles the lockout, making rollbacks progressively more expensive. A fork is finalized when it reaches supermajority (66.7%+ of stake).
A time window during which a designated leader validator can produce a block. Each slot lasts approximately 400 milliseconds. Slots are numbered sequentially from genesis and grouped into epochs of 432,000 slots (~2-3 days). Not every slot produces a block—a skipped slot means the leader was offline or too slow.
A period of 432,000 slots (approximately 2-3 days) that defines a staking cycle. At each epoch boundary, the leader schedule is recalculated based on stake weights, stake activations/deactivations take effect, and inflation rewards are distributed to validators and delegators.