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Stable release v32.1bitcoin/bitcoin · f0de87f04062 ↗3,020 source files · 47.5 MB stored on the server440 file guides

Release published 2026-10-28 · Snapshot fetched 2026-11-01. Latest stable release at fetch time; development branches and Git history are excluded. Only the selected code window and visible folders load here.

bitcoin / bitcoinstable

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bitcoin / doc / policy / mempool-replacements.md

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1# Mempool Replacements
2
3## Current Replace-by-Fee Policy
4
5A transaction conflicts with an in-mempool transaction ("directly conflicting transaction") if they
6spend one or more of the same inputs. A transaction may conflict with multiple in-mempool
7transactions.
8
9A transaction ("replacement transaction") may replace its directly conflicting transactions and
10their in-mempool descendants (together, "original transactions") if, in addition to passing all
11other consensus and policy rules, each of the following conditions are met:
12
131. (Removed)
14
152. (Removed)
16
173. The replacement transaction pays an absolute fee of at least the sum paid by the original
18   transactions.
19
20   *Rationale*: Only requiring the replacement transaction to have a higher feerate could allow an
21   attacker to bypass node minimum relay feerate requirements and cause the network to repeatedly
22   relay slightly smaller replacement transactions without adding any more fees. Additionally, if
23   any of the original transactions would be included in the next block assembled by an economically
24   rational miner, a replacement policy allowing the replacement transaction to decrease the absolute
25   fees in the next block would be incentive-incompatible.
26
274. The additional fees (difference between absolute fee paid by the replacement transaction and the
28   sum paid by the original transactions) pays for the replacement transaction's bandwidth at or
29   above the rate set by the node's incremental relay feerate. For example, if the incremental relay
30   feerate is 0.1 satoshi/vB and the replacement transaction is 500 virtual bytes total, then the
31   replacement pays a fee at least 50 satoshis higher than the sum of the original transactions.
32
33   *Rationale*: Try to prevent DoS attacks where an attacker causes the network to repeatedly relay
34   transactions each paying a tiny additional amount in fees, e.g. just 1 satoshi.
35
365. The number of distinct clusters corresponding to conflicting transactions does not exceed 100.
37
38   *Rationale*: Limit CPU usage required to update the mempool for so many transactions being
39   removed at once.
40
416. The feerate diagram of the mempool must be strictly improved by the replacement transaction.
42
43   *Rationale*: This ensures that block fees in all future blocks will go up
44   after the replacement (ignoring tail effects at the end of a block).
45
46
47## History
48
49* Opt-in full replace-by-fee (without inherited signaling) honoured in mempool and mining as of
50  **v0.12.0** ([PR 6871](https://github.com/bitcoin/bitcoin/pull/6871)).
51
52* [BIP125](https://github.com/bitcoin/bips/blob/master/bip-0125.mediawiki) defined based on
53  Bitcoin Core implementation.
54
55* The incremental relay feerate used to calculate the required additional fees is distinct from
56  `-minrelaytxfee` and configurable using `-incrementalrelayfee`
57  ([PR #9380](https://github.com/bitcoin/bitcoin/pull/9380)).
58
59* RBF enabled by default in the wallet GUI as of **v0.18.1** ([PR
60  #11605](https://github.com/bitcoin/bitcoin/pull/11605)).
61
62* Full replace-by-fee enabled as a configurable mempool policy as of **v24.0** ([PR
63  #25353](https://github.com/bitcoin/bitcoin/pull/25353)).
64
65* Full replace-by-fee is the default policy as of **v28.0** ([PR #30493](https://github.com/bitcoin/bitcoin/pull/30493)).
66
67* Signaling for replace-by-fee is no longer required as of [PR 30592](https://github.com/bitcoin/bitcoin/pull/30592).
68
69* The incremental relay feerate default is 0.1sat/vB ([PR #33106](https://github.com/bitcoin/bitcoin/pull/33106)).
70
71* Feerate diagram policy enabled in conjunction with switch to cluster mempool as of **v31.0**.
72

A READING COMPANION

Source available. Guide coming next.

This file is included in the stable source snapshot. A file-specific guide has not been published yet.

440 guided files · 2,580 pending. Guides cover key sections, not every line.

cmake/bitcoin-build-config.h.in src/consensus/amount.h src/consensus/consensus.h src/primitives/block.h src/primitives/transaction.h src/crypto/sha256.h src/util/moneystr.h src/clientversion.h src/uint256.h src/script/script.h src/policy/policy.h CMakeLists.txt README.md COPYING src/consensus/tx_check.cpp src/consensus/tx_verify.cpp src/consensus/merkle.cpp src/pow.cpp src/validation.cpp src/script/interpreter.cpp src/script/solver.cpp src/script/sign.cpp src/key_io.cpp src/net.cpp src/net_processing.cpp src/netaddress.cpp src/protocol.h src/wallet/wallet.cpp src/wallet/spend.cpp

Code page 1

src/wallet/receive.cpp

src/wallet/coinselection.cpp

src/wallet/fees.cpp

src/wallet/load.cpp

src/txmempool.cpp

src/node/miner.cpp

src/chainparams.cpp

src/consensus/validation.h

src/primitives/transaction.cpp

src/script/descriptor.cpp

src/bitcoin-cli.cpp

src/rpc/blockchain.cpp

src/rpc/rawtransaction.cpp

src/crypto/sha256.cpp

src/serialize.h

src/consensus/merkle.h

src/consensus/tx_check.h

src/consensus/tx_verify.h

src/policy/feerate.h

src/policy/feerate.cpp

src/primitives/transaction_identifier.h

src/chainparamsbase.h

src/chainparamsbase.cpp

src/util/moneystr.cpp

src/crypto/ripemd160.h

src/crypto/sha1.h

src/crypto/sha512.h

src/crypto/hmac_sha256.h

src/crypto/hmac_sha512.h

src/crypto/hmac_sha256.cpp

src/crypto/hmac_sha512.cpp

src/crypto/hkdf_sha256_32.h

src/crypto/hkdf_sha256_32.cpp

src/support/cleanse.h

src/support/cleanse.cpp

src/arith_uint256.h

src/blockencodings.h

src/blockfilter.h

src/crypto/siphash.h

src/crypto/siphash.cpp

src/crypto/muhash.h

src/crypto/chacha20.h

src/crypto/poly1305.h

src/crypto/chacha20poly1305.h

src/crypto/chacha20poly1305.cpp

src/compressor.h

src/compressor.cpp

src/flatfile.cpp

src/dbwrapper.h

src/util/chaintype.h

src/util/chaintype.cpp

src/scheduler.h

src/scheduler.cpp

src/checkqueue.h

src/threadsafety.h

src/util/obfuscation.h

src/util/byte_units.h

src/util/overflow.h

src/blockencodings.cpp

src/blockfilter.cpp

src/merkleblock.cpp

src/merkleblock.h

src/addrman.cpp

src/netgroup.cpp

src/net_permissions.cpp

src/netbase.cpp

src/torcontrol.cpp

src/net_types.h

src/net_types.cpp

src/policy/packages.cpp

src/policy/rbf.cpp

src/policy/truc_policy.cpp

src/policy/ephemeral_policy.cpp

src/policy/settings.cpp

src/policy/policy.cpp

src/node/transaction.cpp

src/node/coin.cpp

src/rpc/client.cpp

src/rpc/external_signer.cpp

src/rpc/request.cpp

src/rpc/server_util.cpp

src/rpc/fees.cpp

src/rpc/output_script.cpp

src/rpc/rawtransaction_util.cpp

src/rpc/server.cpp

src/rpc/mempool.cpp

src/rpc/mining.cpp

src/rpc/net.cpp

src/rpc/node.cpp

src/rpc/blockchain.h

src/rpc/client.h

src/rpc/mempool.h

src/rpc/mining.h

src/rpc/rawtransaction_util.h

src/rpc/register.h

src/rpc/request.h

src/rpc/server_util.h

src/rpc/protocol.h

src/rpc/server.h

src/rpc/signmessage.cpp

src/rpc/txoutproof.cpp

src/rpc/util.cpp

src/wallet/rpc/addresses.cpp

src/wallet/rpc/backup.cpp

src/wallet/rpc/coins.cpp

src/wallet/rpc/encrypt.cpp

src/wallet/rpc/signmessage.cpp

src/wallet/rpc/util.cpp

src/wallet/rpc/util.h

src/wallet/coincontrol.cpp

src/wallet/coincontrol.h

src/wallet/context.cpp

src/wallet/context.h

src/wallet/crypter.cpp

src/wallet/crypter.h

src/wallet/db.cpp

src/wallet/export.cpp

src/wallet/external_signer_scriptpubkeyman.cpp

src/wallet/rpc/spend.cpp

src/wallet/rpc/transactions.cpp

src/wallet/rpc/wallet.cpp

src/wallet/feebumper.cpp

src/wallet/feebumper.h

src/index/base.h

src/index/base.cpp

src/index/txindex.h

src/index/txindex.cpp

src/index/txindex_key.h

src/index/txospenderindex.h

src/index/txospenderindex.cpp

src/index/blockfilterindex.h

src/index/blockfilterindex.cpp

src/index/coinstatsindex.h

src/index/coinstatsindex.cpp

src/index/db_key.h

src/index/disktxpos.h

src/kernel/chain.cpp

src/kernel/chain.h

src/kernel/checks.cpp

src/kernel/checks.h

src/kernel/context.cpp

src/kernel/context.h

src/kernel/cs_main.cpp

src/kernel/cs_main.h

src/kernel/disconnected_transactions.cpp

src/kernel/disconnected_transactions.h

src/kernel/mempool_removal_reason.cpp

src/kernel/mempool_removal_reason.h

src/kernel/coinstats.cpp

src/kernel/coinstats.h

src/kernel/chainparams.cpp

src/kernel/chainparams.h

src/wallet/sqlite.cpp

src/wallet/sqlite.h

src/wallet/transaction.cpp

src/wallet/transaction.h

src/wallet/dump.cpp

src/wallet/dump.h

src/wallet/init.cpp

src/wallet/walletutil.cpp

src/wallet/walletutil.h

src/wallet/wallettool.cpp

src/wallet/wallettool.h

src/wallet/export.h

src/wallet/migrate.cpp

src/wallet/migrate.h

src/wallet/db.h

src/wallet/walletdb.cpp

src/wallet/interfaces.cpp

src/wallet/scriptpubkeyman.cpp

src/wallet/scriptpubkeyman.h

src/kernel/bitcoinkernel.cpp

src/kernel/bitcoinkernel.h

src/kernel/bitcoinkernel_wrapper.h

src/node/abort.cpp

src/node/abort.h

src/node/caches.cpp

src/node/caches.h

src/kernel/caches.h

src/node/chainstate.cpp

src/node/chainstate.h

src/node/blockstorage.cpp

src/node/blockstorage.h

src/node/mempool_persist.cpp

src/node/mempool_persist.h

src/node/utxo_snapshot.cpp

src/node/utxo_snapshot.h

src/node/kernel_notifications.cpp

src/node/kernel_notifications.h

src/node/blockmanager_args.cpp

src/kernel/blockmanager_opts.h

src/util/expected.cpp

src/policy/settings.h

src/util/types.h

src/kernel/messagestartchars.h

src/kernel/warning.h

src/util/exception.h

src/common/license_info.h

src/node/coins_view_args.h

src/node/database_args.h

src/util/batchpriority.h

src/util/ui_change_type.h

src/node/coins_view_args.cpp

src/node/peerman_args.h

src/util/serfloat.h

src/node/blockmanager_args.h

src/node/database_args.cpp

src/util/overloaded.h

src/util/rbf.cpp

src/util/thread.h

src/common/netif.h

src/common/url.h

src/interfaces/types.h

src/node/chainstatemanager_args.h

src/node/minisketchwrapper.h

src/util/macros.h

src/util/syserror.h

src/common/run_command.h

src/util/bytevectorhash.cpp

src/node/mempool_persist_args.cpp

src/util/exec.h

src/crypto/hex_base.h

src/node/mempool_persist_args.h

src/interfaces/echo.h

src/util/batchpriority.cpp

src/util/threadnames.h

src/node/coin.h

src/node/mempool_args.h

src/util/asmap.h

src/util/bytevectorhash.h

src/node/context.cpp

src/util/insert.h

src/util/readwritefile.h

src/util/thread.cpp

src/kernel/types.h

src/interfaces/rpc.h

src/util/fees.cpp

src/node/peerman_args.cpp

src/node/interface_ui.cpp

src/interfaces/handler.h

src/node/mining_args.h

src/util/hasher.cpp

src/common/init.h

src/kernel/mempool_limits.h

src/common/system.h

src/crypto/sha3.h

src/util/threadinterrupt.cpp

src/node/protocol_version.h

src/util/exception.cpp

src/common/messages.h

src/node/connection_types.cpp

src/util/bip32.h

src/common/license_info.cpp

src/util/stdmutex.h

src/common/run_command.cpp

src/util/check.cpp

src/util/golombrice.h

src/node/types.h

src/node/timeoffsets.h

src/util/readwritefile.cpp

src/util/fastrange.h

src/util/signalinterrupt.h

src/util/task_runner.h

src/util/syserror.cpp

src/common/interfaces.cpp

src/common/types.h

src/util/threadinterrupt.h

src/kernel/chainstatemanager_opts.h

src/node/psbt.h

src/policy/ephemeral_policy.h

src/util/trace.h

src/common/url.cpp

src/kernel/mempool_options.h

src/util/serfloat.cpp

src/kernel/notifications_interface.h

src/node/timeoffsets.cpp

src/node/warnings.cpp

src/util/hash_type.h

src/crypto/hex_base.cpp

src/node/eviction.h

src/util/tokenbucket.h

src/crypto/aes.h

src/common/pcp.h

src/util/feefrac.cpp

src/node/transaction.h

src/util/threadnames.cpp

src/common/signmessage.h

src/util/exec.cpp

src/util/signalinterrupt.cpp

src/attributes.h

src/chainparams.h

src/clientversion.cpp

src/common/signmessage.cpp

src/compat/assumptions.h

src/compat/byteswap.h

src/compat/cpuid.h

src/compat/endian.h

src/compat/stdin.cpp

src/compat/stdin.h

src/core_memusage.h

src/crypto/common.h

src/deploymentinfo.cpp

src/deploymentinfo.h

src/deploymentstatus.cpp

src/deploymentstatus.h

src/dummywallet.cpp

src/external_signer.h

src/indirectmap.h

src/init/basic.cpp

src/init/bitcoin-gui.cpp

src/init/bitcoin-node.cpp

src/init/bitcoin-qt.cpp

src/init/bitcoin-wallet.cpp

src/init/bitcoind.cpp

src/init/common.h

src/interfaces/init.h

src/interfaces/ipc.h

src/logging/categories.h

src/logging/timer.h

src/net_permissions.h

src/netmessagemaker.h

src/node/chainstatemanager_args.cpp

src/node/connection_types.h

src/node/context.h

src/node/interface_ui.h

src/node/mempool_args.cpp

src/node/mining_args.cpp

src/node/minisketchwrapper.cpp

src/node/txreconciliation.h

src/node/warnings.h

src/outputtype.cpp

src/outputtype.h

src/policy/fees/estimator_args.cpp

src/policy/fees/estimator_args.h

src/policy/fees/estimator_man.cpp

src/policy/fees/estimator_man.h

src/policy/packages.h

src/policy/rbf.h

src/policy/truc_policy.h

src/primitives/block.cpp

src/randomenv.h

src/script/keyorigin.h

src/script/parsing.cpp

src/script/parsing.h

src/script/script_error.h

src/script/sigcache.cpp

src/script/sigcache.h

src/script/solver.h

src/script/verify_flags.h

src/semaphore_grant.h

src/support/allocators/secure.h

src/support/allocators/zeroafterfree.h

src/uint256.cpp

src/util/bip32.cpp

src/util/fees.h

src/util/fs.cpp

src/util/result.h

src/util/string.cpp

src/util/tokenpipe.cpp

src/util/translation.h

src/util/vector.h

src/versionbits.h

src/versionbits_impl.h

src/wallet/external_signer_scriptpubkeyman.h

src/wallet/fees.h

src/wallet/load.h

src/wallet/receive.h

src/wallet/rpc/wallet.h

src/wallet/types.h

src/walletinitinterface.h

src/zmq/zmqabstractnotifier.cpp

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