Glossary · Consensus

Slot.

A one-second unit of time in Ouroboros consensus. Each slot may produce a block.

Think of it as

One second of Cardano's heartbeat. Most ticks do nothing; on average, one in twenty produces a block.

In depth

Cardano time is divided into one-second slots. In each slot a leader may be elected via Ouroboros Praos, with probability proportional to stake. Many slots remain empty by design; on average a block is produced every 20 seconds. Validity ranges in transactions are expressed in slots.

Example

A transaction with validity range "slot 1000–1200" can only be included in a block produced during those 200 seconds.

Next on this path

  1. Block An ordered batch of transactions appended to the chain by the slot leader.
  2. Ouroboros Cardano’s family of proof-of-stake consensus protocols.
  3. Epoch A five-day window on Cardano during which staking distribution is fixed.