A block that has received votes from validators representing a supermajority (66.7%+) of the cluster's active stake, achieving optimistic confirmation. Confirmed blocks are highly likely to be finalized but are not yet irreversible — full finality requires the block to become rooted through 31+ consecutive confirmations in Tower BFT.
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A block that has received votes from validators representing a supermajority (66.7%+) of the cluster's active stake, achieving optimistic confirmation. Confirmed blocks are highly likely to be finalized but are not yet irreversible — full finality requires the block to become rooted through 31+ consecutive confirmations in Tower BFT.
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Consensus, leader rotation, slots, epochs, and the runtime.
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Confirmed Block (confirmed-block) Category: Core Protocol Definition: A block that has received votes from validators representing a supermajority (66.7%+) of the cluster's active stake, achieving optimistic confirmation. Confirmed blocks are highly likely to be finalized but are not yet irreversible — full finality requires the block to become rooted through 31+ consecutive confirmations in Tower BFT. Related: Block, Optimistic Confirmation, Supermajority, Rooted
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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.
A transaction confirmation level achieved when 66.7%+ of total stake has voted on the slot, typically within ~400ms. Optimistic confirmation provides high probability of finality without waiting for full root depth. It corresponds to the 'confirmed' commitment level in RPC queries.
A threshold of more than 2/3 (66.7%) of total active stake agreeing on a particular fork. Supermajority is required for optimistic confirmation and, through sustained voting, for finality (rooting). If supermajority is lost (e.g., too many validators offline), the cluster halts until it recovers.
A slot that has been finalized by achieving maximum lockout in Tower BFT—meaning 31+ consecutive confirmations have been built on top of it. Once rooted, a slot and its transactions are considered irreversible. Rooted corresponds to the 'finalized' commitment level and takes approximately 12-13 seconds.
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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.
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.
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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.
A transaction confirmation level achieved when 66.7%+ of total stake has voted on the slot, typically within ~400ms. Optimistic confirmation provides high probability of finality without waiting for full root depth. It corresponds to the 'confirmed' commitment level in RPC queries.
A threshold of more than 2/3 (66.7%) of total active stake agreeing on a particular fork. Supermajority is required for optimistic confirmation and, through sustained voting, for finality (rooting). If supermajority is lost (e.g., too many validators offline), the cluster halts until it recovers.
A slot that has been finalized by achieving maximum lockout in Tower BFT—meaning 31+ consecutive confirmations have been built on top of it. Once rooted, a slot and its transactions are considered irreversible. Rooted corresponds to the 'finalized' commitment level and takes approximately 12-13 seconds.
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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 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.