Stellar Proof-of-Agreement: How SCP Consensus Works (Not Proof of Stake)

Search for how Stellar reaches consensus and you will find a lot of confusion — people assume it must be proof of stake like Ethereum. It is not. Stellar usesProof-of-Agreement (PoA): consensus reached through the Stellar Consensus Protocol (SCP), a federated Byzantine agreement system with no mining, no staking, and no elected leader. Here is how it actually works, based on theSDF's Proof-of-Agreement explainer.

Not PoW, not PoS — federated agreement

Proof of work burns energy to elect a block producer; proof of stake elects one based on locked tokens. SCP does neither. Instead, every validator votes on what the next ledger contains, and the network finalizes a ledger when aquorum — an overlapping web of trusted validators — agrees. There is no competition to win the next block; agreement is reached cooperatively roughly every 5 seconds.

Quorum slices: trust is chosen, not assigned

Each validator declares a quorum slice — the set of other validators it trusts. Your node accepts a ledger when your slice reaches agreement, and the network reaches consensus when slices overlap enough to form a quorum. This is what makes SCP federated: trust emerges bottom-up from individual choices rather than top-down from a fixed validator set.

Federated voting in three steps

SCP's vote-commit-accept flow: validators vote for a transaction set,confirm they see their quorum voting the same, and accept it once the quorum does — then externalize it into the closed ledger. If slices are poorly chosen the worst case is a halt (the network pauses) rather than a fork — safety over liveness, the right trade-off for money.

Why this design

No mining means near-zero energy and no fee market wars; ~5-second ledgers with true finality means payments settle fast and stay settled — why Stellar is built for payments and remittances. The cost: validators earn no rewards, so the network relies on aligned incentives — businesses (anchors, exchanges, wallets) run validators to protect their own infrastructure.

Run a validator yourself

Anyone can run stellar-core — see ourvalidator node setup guide. Your votes count once established operators include you in their quorum slices, so reliable uptime is how you earn real influence.

Keep learning

SDF: Proof-of-Agreement ·SCP glossary ·Federated Byzantine Agreement ·Run a validator ·Stellar hub ·Stellar Network masterclass

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