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1v31.0 Release Notes
2===================
3
4Bitcoin Core version 31.0 is now available from:
5
6  <https://bitcoincore.org/bin/bitcoin-core-31.0/>
7
8This release includes new features, various bug fixes and performance
9improvements, as well as updated translations.
10
11Please report bugs using the issue tracker at GitHub:
12
13  <https://github.com/bitcoin/bitcoin/issues>
14
15To receive security and update notifications, please subscribe to:
16
17  <https://bitcoincore.org/en/list/announcements/join/>
18
19
20With the release of this new major version, versions `28.x` and
21older are at "End of Life" and will no longer receive updates.
22
23In accordance with the security policy, we will in two weeks disclose:
24
25* Medium and high severity vulnerabilities fixed in `29.0`. There is one of these.
26
27* Low severity vulnerabilities fixed in `31.0`. There are none of these.
28
29How to Upgrade
30==============
31
32If you are running an older version, shut it down. Wait until it has completely
33shut down (which might take a few minutes in some cases), then run the installer
34(on Windows) or just copy over `/Applications/Bitcoin-Qt` (on macOS) or
35`bitcoind`/`bitcoin-qt` (on Linux).
36
37Upgrading directly from a version of Bitcoin Core that has reached its EOL is
38possible, but it might take some time if the data directory needs to be
39migrated. Old wallet versions of Bitcoin Core are generally supported.
40
41Compatibility
42==============
43
44Bitcoin Core is supported and tested on the following operating systems or
45newer: Linux Kernel 3.17, macOS 14, and Windows 10 (version 1903). Bitcoin Core
46should also work on most other Unix-like systems but is not as frequently tested
47on them. It is not recommended to use Bitcoin Core on unsupported systems.
48
49Notable changes
50===============
51
52The default `-dbcache` value has been increased to 1024 MiB from 450 MiB on
53systems where at least 4096 MiB of RAM is detected. This improves performance
54but increases memory usage. On some systems (for example when running in
55containers), the detected RAM may exceed the memory actually available, which
56can lead to out-of-memory conditions. To maintain the previous behavior, set
57`-dbcache=450`. See
58[reduce-memory.md](https://github.com/bitcoin/bitcoin/blob/master/doc/reduce-memory.md)
59for further guidance on low-memory systems. (#34692)
60
61Mempool
62-------
63
64The mempool has been reimplemented with a new design ("cluster mempool"), to
65facilitate better decision-making when constructing block templates, evicting
66transactions, relaying transactions, and validating replacement transactions
67(RBF). Most changes should be transparent to users, but some behavior changes
68are noted:
69
70- The mempool no longer enforces ancestor or descendant size/count limits.
71Instead, two new default policy limits are introduced governing connected
72components, or clusters, in the mempool, limiting clusters to 64 transactions
73and up to 101 kB in virtual size.  Transactions are considered to be in the same
74cluster if they are connected to each other via any combination of parent/child
75relationships in the mempool. These limits can be overridden using command-line
76arguments; see the extended help (`-help-debug`) for more information.
77
78- Within the mempool, transactions are ordered based on the feerate at which
79they are expected to be mined, which takes into account the full set, or
80"chunk", of transactions that would be included together (e.g., a parent and its
81child, or more complicated subsets of transactions). This ordering is utilized
82by the algorithms that implement transaction selection for constructing block
83templates; eviction from the mempool when it is full; and transaction relay
84announcements to peers.
85
86- The replace-by-fee validation logic has been updated so that transaction
87replacements are only accepted if the resulting mempool's feerate diagram is
88strictly better than before the replacement. This eliminates all known cases of
89replacements occurring that make the mempool worse off, which was possible under
90previous RBF rules. For singleton transactions (that are in clusters by
91themselves) it's sufficient for a replacement to have a higher fee and feerate
92than the original. See [delvingbitcoin.org
93post](https://delvingbitcoin.org/t/an-overview-of-the-cluster-mempool-proposal/393#rbf-can-now-be-made-incentive-compatible-for-miners-11)
94for more information.
95
96- Two new RPCs have been added: `getmempoolcluster` will provide the set of
97transactions in the same cluster as the given transaction, along with the
98ordering of those transactions and grouping into chunks; and
99`getmempoolfeeratediagram` will return the feerate diagram of the entire
100mempool.
101
102- Chunk size and chunk fees are now also included in the output of
103`getmempoolentry`.
104
105- The "CPFP Carveout" has been removed from the mempool logic. The CPFP carveout
106allowed one additional child transaction to be added to a package that's already
107at its descendant limit, but only if that child has exactly one ancestor (the
108package's root) and is small (no larger than 10kvB). Nothing is allowed to
109bypass the cluster count limit. It is expected that smart contracting use-cases
110requiring similar functionality employ TRUC transactions and sibling eviction
111instead going forward.
112
113- Some additional discussion can be found at
114[doc/policy/mempool-terminology.md](https://github.com/bitcoin/bitcoin/blob/master/doc/policy/mempool-terminology.md)
115and
116[doc/policy/mempool-replacements.md](https://github.com/bitcoin/bitcoin/blob/master/doc/policy/mempool-replacements.md).
117
118P2P and network changes
119-----------------------
120
121- Normally local transactions are broadcast to all connected peers with which we
122do transaction relay. Now, for the `sendrawtransaction` RPC this behavior can be
123changed to only do the broadcast via the Tor or I2P networks. A new boolean
124option `-privatebroadcast` has been added to enable this behavior. This improves
125the privacy of the transaction originator in two aspects:
126  1. Their IP address (and thus geolocation) is never known to the recipients.
127  2. If the originator sends two otherwise unrelated transactions, they will not
128  be linkable. This is because a separate connection is used for broadcasting
129  each transaction. (#29415)
130
131- New RPCs have been added to introspect and control private broadcast:
132`getprivatebroadcastinfo` reports transactions currently being privately
133broadcast, and `abortprivatebroadcast` removes matching transactions from the
134private broadcast queue. (#34329)
135
136- Transactions participating in one-parent-one-child package relay can now have
137the parent with a feerate lower than the `-minrelaytxfee` feerate, even 0 fee.
138This expands the change from 28.0 to also cover packages of non-TRUC
139transactions. Note that in general the package child can have additional
140unconfirmed parents, but they must already be in-mempool for the new package to
141be relayed. (#33892)
142
143- The release has asmap data embedded for the first time, allowing the asmap
144feature to be used without any externally sourced file. The embedded map [was
145created on 2026-03-05](https://github.com/bitcoin/bitcoin/pull/34696). Despite
146the data being available, the option remains off-by-default. Users still need to
147set `-asmap` or `-asmap=1` explicitly to make it possible to use a peer's ASN
148(ISP/hoster identifier) in netgroup bucketing in order to ensure a higher
149diversity in their peer set.
150
151Updated RPCs
152------------
153
154- `gettxspendingprevout` has 2 new optional arguments: `mempool_only` and
155`return_spending_tx`. If `mempool_only` is true it will limit scans to the
156mempool even if `txospenderindex` is available. If `return_spending_tx` is true,
157the full spending tx will be returned. In addition if `txospenderindex` is
158available and a confirmed spending transaction is found, its block hash will be
159returned. (#24539)
160
161- The `getpeerinfo` RPC no longer returns the `startingheight` field unless the
162configuration option `-deprecatedrpc=startingheight` is used. The
163`startingheight` field will be fully removed in the next major release. (#34197)
164
165- The `getblock` RPC now returns a `coinbase_tx` object at verbosity levels 1,
1662, and 3. It contains `version`, `locktime`, `sequence`, `coinbase` and
167`witness`. This allows for efficiently querying coinbase transaction properties
168without fetching the full transaction data at verbosity 2+. (#34512)
169
170REST API
171--------
172
173- A new REST API endpoint
174(`/rest/blockpart/<BLOCK-HASH>.<bin|hex>?offset=<OFFSET>&size=<SIZE>`) has been
175introduced for efficiently fetching a range of bytes from block `<BLOCK-HASH>`.
176(#33657)
177
178Build System
179------------
180
181- The minimum supported Clang compiler version has been raised to 17.0 (#33555).
182- The minimum supported GCC compiler version has been raised to 12.1 (#33842).
183
184Updated settings
185----------------
186
187- The `-paytxfee` startup option and the `settxfee` RPC are now deleted after
188being deprecated in Bitcoin Core 30.0. They used to allow the user to set a
189static fee rate for wallet transactions, which could potentially lead to
190overpaying or underpaying. Users should instead rely on fee estimation or
191specify a fee rate per transaction using the `fee_rate` argument in RPCs such as
192`fundrawtransaction`, `sendtoaddress`, `send`, `sendall`, and `sendmany`.
193(#32138)
194
195- Specifying `-asmap` or `-asmap=1` will load the embedded asmap data instead of
196an external file. In previous releases, if `-asmap` was specified without a
197filename, this would try to load an `ip_asn.map` data file. Now loading an
198external asmap file always requires an explicit filename like
199`-asmap=ip_asn.map`.
200
201- The `-maxorphantx` startup option has been removed. It was previously
202deprecated and has no effect anymore since v30.0. (#33872)
203
204- `tor` has been removed as a network specification. It was deprecated in favour
205of `onion` in v0.17.0. (#34031)
206
207- When `-logsourcelocations` is enabled, the log output now contains just the
208function name instead of the entire function signature. (#34088)
209
210- The default `-dbcache` value has been increased to `1024` MiB from `450` MiB
211on systems where at least `4096` MiB of RAM is detected. This is a performance
212increase, but will use more memory. To maintain the previous behaviour, set
213`-dbcache=450`. (#34692)
214
215- `-privatebroadcast` is added to enable private broadcast behavior for
216`sendrawtransaction`.
217
218New settings
219------------
220
221- `-txospenderindex` enables the creation of a transaction output spender index
222that, if present, will be scanned by `gettxspendingprevout` if a spending
223transaction was not found in the mempool. (#24539)
224
225GUI changes
226-----------
227
228- The GUI has been updated to Qt 6.8. (#34650)
229
230- The `createwallet`, `createwalletdescriptor` and `migratewallet` commands are
231filtered from the console history to improve security and privacy. (gui#901)
232
233- The Restore Wallet dialog shows an error message if the restored wallet name
234is empty. (gui#924)
235
236Fee Estimation
237--------------
238
239The Bitcoin Core fee estimator minimum fee rate bucket was updated from **1
240sat/vB** to **0.1 sat/vB**, which matches the node’s default `minrelaytxfee`. This
241means that for a given confirmation target, if a sub-1 sat/vB fee rate bucket is
242the minimum tracked with sufficient data, its average value will be returned as
243the fee rate estimate.
244
245Restarting a node with this change invalidates previously saved
246estimates in `fee_estimates.dat`, the fee estimator will start tracking fresh
247stats.
248
249IPC Interface
250-------------

src/wallet/receive.cpp

src/wallet/coinselection.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/init.cpp

src/crypto/sha256.cpp

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/crypto/siphash.cpp

src/crypto/muhash.h

src/crypto/chacha20.h

src/crypto/poly1305.h

src/crypto/chacha20poly1305.h

src/crypto/chacha20poly1305.cpp

src/util/chaintype.cpp

src/util/obfuscation.h

src/util/byte_units.h

src/util/overflow.h

src/blockencodings.cpp

src/net_permissions.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/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/rpc/util.h

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/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/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/util/rbf.h

src/crypto/hex_base.h

src/node/mempool_persist_args.h

src/interfaces/echo.h

src/util/any.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/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

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