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TERM_DEF // TRANSACTION / MINIMUM_RELAY_FEE_RATE
MINIMUM RELAY
FEE RATE
Minimum Relay Fee Rate. Mempool floor (default 1 sat/vB) below which transactions are not relayed.

This page sits in the Transaction section — How money moves: inputs, outputs, fees, signatures, sighash flags, and the formats that wrap them. Read on for what it is, why it exists, how it works under the hood, and what to watch out for.
WHAT_MINIMUM_RELAY_FEE_RATE_IS
Minimum Relay Fee Rate — at a glance
TRANSACTION
Minimum Relay Fee Rate is part of the FEE ECONOMY sub-family of transaction-level concepts. The lowest feerate (in sat/kvB) at which a node will relay a transaction onward to its peers. Mempool floor (default 1 sat/vB) below which transactions are not relayed.
Why it exists
DESIGN
Free-tx relay would let attackers flood the network with zero-fee transactions, exhausting bandwidth and mempool memory. The minimum relay fee is the floor that prices basic anti-DoS at a level near the cost of network resources.
HOW_IT_WORKS
Mechanism
HOW IT WORKS
bitcoin-core/">Bitcoin Core defaults to minrelaytxfee=0.00001000 BTC/kvB (= 1 sat/vB). Any tx below this is silently dropped — neither relayed nor stored in the local mempool. The setting is configurable per-node.
1. Wallet selects UTXOs whose total value covers the spend amount + estimated fee (coin selection). 2. Wallet builds the transaction body: version, inputs (each with prev txid + vout + sequence), outputs (each with value + scriptPubKey), locktime. 3. Wallet computes the sighash for each input (which parts of the tx the signature commits to — controlled by the SIGHASH flag). 4. Wallet signs each input with the right private key. Witness/scriptSig is populated with the resulting signatures + pubkeys. 5. Tx is broadcast to peers. Mempool propagation: tens of seconds globally. 6. A miner includes it in a block. Confirmation count grows by 1 per block; after ~6 the tx is effectively final.
WORKED_EXAMPLE
Minimum Relay Fee Rate — FEE ECONOMY
EXAMPLE
default : 1 sat/vB (1,000 sats per kvB) configurable : node operator sets -minrelaytxfee= hard floor : 0 is invalid — Core enforces minimum of 1 sat/kvB effect of bumping it : your node refuses to relay cheaper txs but still validates them in mined blocks opposite end : -maxmempool eviction targets the LOWEST feerate txs first
KEY_PROPERTIES
NODE-LOCAL
Set per-node. Different operators may disagree on the floor; what reaches a miner depends on the route through the network.
ATOMIC
A transaction is either fully accepted into a block or fully rejected. There is no partial spend.
IMMUTABLE INPUTS
A UTXO can only ever be spent once. After that, it is permanently consumed.
NO BALANCES
Bitcoin tracks UTXOs, not balances. Your wallet computes a balance by summing the UTXOs it controls.
COMMON_PITFALLS
Things that catch people out
PITFALLS
  • address-reuse/">Address reuse degrades privacy — every reuse links more of your UTXOs together publicly. Modern wallets generate a fresh address per receive.
  • Fee estimation matters: under-pay and your tx sits in the mempool for hours; over-pay and you tip the miner more than necessary. Use a fee estimator.
  • "Change outputs" must go back to a fresh address you control. A missing output/">change output sends the difference to the miner as fee — a known footgun.
  • RBF (Replace-By-Fee) lets you re-broadcast a tx with a higher fee. Useful for stuck txs but means a 0-confirmation tx is never truly final.
RELATED_CONCEPTS
Other terms from Transaction — click any to read its page:
Transaction (Tx) Raw Transaction Transaction ID (TXID) wTXID (Witness TXID) Input Output UTXO (Unspent Transaction Output) UTXO Set
TERMINOLOGY_INDEX
TERMINOLOGY
Minimum Relay Fee Rate
Mempool floor (default 1 sat/vB) below which transactions are not relayed.
Transaction (Tx)
A signed payload spending one or more UTXOs and creating new ones; every state change in Bitcoin is a tx.
Raw Transaction
The hex-serialized bytes of a transaction, ready to broadcast or analyze.
Transaction ID (TXID)
HASH256 of a transaction's pre-witness serialization; used to reference outputs by (txid, vout).
wTXID (Witness TXID)
HASH256 of the full transaction including witness data; commits to signatures and used in the witness commitment.
Input
A reference to a previous output being spent, plus the data (scriptSig/witness) authorizing the spend.
Output
An (amount, scriptPubKey) pair created by a transaction; spendable later by a tx whose input references it.
UTXO (Unspent Transaction Output)
An output that hasn't been spent yet; your "balance" is the sum of UTXOs you can sign for.