28.0 Release Notes

Bitcoin Core version 28.0 is now available from:

• 🌐 https://bitcoincore.org/bin/bitcoin-core-28.0/
• 🧲 magnet:?xt=urn:btih:e18e92024fc9d4026cf8cdef174f03c24080fd1f&dn=bitcoin-core-28.0&tr=udp%3A%2F%2Ftracker.coppersurfer.tk%3A6969%2Fannounce&tr=udp%3A%2F%2Ftracker.openbittorrent.com%3A80&tr=udp%3A%2F%2Ftracker.opentrackr.org%3A1337%2Fannounce&tr=udp%3A%2F%2Ftracker.torrent.eu.org%3A451%2Fannounce&tr=udp%3A%2F%2Ftracker.leechers-paradise.org%3A6969%2Fannounce&tr=udp%3A%2F%2Fexplodie.org%3A6969%2Fannounce&tr=udp%3A%2F%2Ftracker.bitcoin.sprovoost.nl%3A6969&ws=http://bitcoincore.org/bin/

This release includes new features, various bug fixes and performance improvements, as well as updated translations.

Please report bugs using the issue tracker at GitHub:

https://github.com/bitcoin/bitcoin/issues

To receive security and update notifications, please subscribe to:

https://bitcoincore.org/en/list/announcements/join/

How to Upgrade

If you are running an older version, shut it down. Wait until it has completely shut down (which might take a few minutes in some cases), then run the installer (on Windows) or just copy over /Applications/Bitcoin-Qt (on macOS) or bitcoind/bitcoin-qt (on Linux).

Upgrading directly from a version of Bitcoin Core that has reached its EOL is possible, but it might take some time if the data directory needs to be migrated. Old wallet versions of Bitcoin Core are generally supported.

Running Bitcoin Core binaries on macOS requires self signing.

cd /path/to/bitcoin-28.0/bin
xattr -d com.apple.quarantine bitcoin-cli bitcoin-qt bitcoin-tx bitcoin-util bitcoin-wallet bitcoind test_bitcoin
codesign -s - bitcoin-cli bitcoin-qt bitcoin-tx bitcoin-util bitcoin-wallet bitcoind test_bitcoin

Compatibility

Bitcoin Core is supported and extensively tested on operating systems using the Linux Kernel 3.17+, macOS 11.0+, and Windows 7 and newer. Bitcoin Core should also work on most other UNIX-like systems but is not as frequently tested on them. It is not recommended to use Bitcoin Core on unsupported systems.

Notable changes

Testnet4/BIP94 support

Support for Testnet4 as specified in BIP94 has been added. The network can be selected with the -testnet4 option and the section header is also named [testnet4].

While the intention is to phase out support for Testnet3 in an upcoming version, support for it is still available via the known options in this release. (#29775)

Windows Data Directory

The default data directory on Windows has been moved from C:\Users\Username\AppData\Roaming\Bitcoin to C:\Users\Username\AppData\Local\Bitcoin. Bitcoin Core will check the existence of the old directory first and continue to use that directory for backwards compatibility if it is present. (#27064)

JSON-RPC 2.0 Support

The JSON-RPC server now recognizes JSON-RPC 2.0 requests and responds with strict adherence to the specification. See JSON-RPC-interface.md for details. (#27101)

JSON-RPC clients may need to be updated to be compatible with the JSON-RPC server. Please open an issue on GitHub if any compatibility issues are found.

libbitcoinconsensus Removal

The libbitcoin-consensus library was deprecated in 27.0 and is now completely removed. (#29648)

P2P and Network Changes

• Previously if Bitcoin Core was listening for P2P connections, either using default settings or via bind=addr:port it would always also bind to 127.0.0.1:8334 to listen for Tor connections. It was not possible to switch this off, even if the node didn't use Tor. This has been changed and now bind=addr:port results in binding on addr:port only. The default behavior of binding to 0.0.0.0:8333 and 127.0.0.1:8334 has not been changed.

  If you are using a bind=... configuration without bind=...=onion and rely on the previous implied behavior to accept incoming Tor connections at 127.0.0.1:8334, you need to now make this explicit by using bind=... bind=127.0.0.1:8334=onion. (#22729)

• Bitcoin Core will now fail to start up if any of its P2P binds fail, rather than the previous behaviour where it would only abort startup if all P2P binds had failed. (#22729)

• UNIX domain sockets can now be used for proxy connections. Set -onion or -proxy to the local socket path with the prefix unix: (e.g. -onion=unix:/home/me/torsocket). (#27375)

• UNIX socket paths are now accepted for -zmqpubrawblock and -zmqpubrawtx with the format -zmqpubrawtx=unix:/path/to/file (#27679)

• Additional "in" and "out" flags have been added to -whitelist to control whether permissions apply to inbound connections and/or manual ones (default: inbound only). (#27114)

• Transactions having a feerate that is too low will be opportunistically paired with their child transactions and submitted as a package, thus enabling the node to download 1-parent-1-child packages using the existing transaction relay protocol. Combined with other mempool policies, this change allows limited "package relay" when a parent transaction is below the mempool minimum feerate. Topologically Restricted Until Confirmation (TRUC) parents are additionally allowed to be below the minimum relay feerate (i.e., pay 0 fees). Use the submitpackage RPC to submit packages directly to the node. Warning: this P2P feature is limited (unlike the submitpackage interface, a child with multiple unconfirmed parents is not supported) and not yet reliable under adversarial conditions. (#28970)

Mempool Policy Changes

• Transactions with version number set to 3 are now treated as standard on all networks (#29496), subject to opt-in Topologically Restricted Until Confirmation (TRUC) transaction policy as described in BIP 431. The policy includes limits on spending unconfirmed outputs (#28948), eviction of a previous descendant if a more incentive-compatible one is submitted (#29306), and a maximum transaction size of 10,000vB (#29873). These restrictions simplify the assessment of incentive compatibility of accepting or replacing TRUC transactions, thus ensuring any replacements are more profitable for the node and making fee-bumping more reliable.

• Pay To Anchor (P2A) is a new standard witness output type for spending, a newly recognised output template. This allows for key-less anchor outputs, with compact spending conditions for additional efficiencies on top of an equivalent sh(OP_TRUE) output, in addition to the txid stability of the spending transaction. N.B. propagation of this output spending on the network will be limited until a sufficient number of nodes on the network adopt this upgrade. (#30352)

• Limited package RBF is now enabled, where the proposed conflicting package would result in a connected component, aka cluster, of size 2 in the mempool. All clusters being conflicted against must be of size 2 or lower. (#28984)

• The default value of the -mempoolfullrbf configuration option has been changed from 0 to 1, i.e. mempoolfullrbf=1. (#30493)

Updated RPCs

• The dumptxoutset RPC now returns the UTXO set dump in a new and improved format. Correspondingly, the loadtxoutset RPC now expects this new format in the dumps it tries to load. Dumps with the old format are no longer supported and need to be recreated using the new format to be usable. (#29612)

• AssumeUTXO mainnet parameters have been added for height 840,000. This means the loadtxoutset RPC can now be used on mainnet with the matching UTXO set from that height. (#28553)

• The warnings field in getblockchaininfo, getmininginfo and getnetworkinfo now returns all the active node warnings as an array of strings, instead of a single warning. The current behaviour can be temporarily restored by running Bitcoin Core with the configuration option -deprecatedrpc=warnings. (#29845)

• Previously when using the sendrawtransaction RPC and specifying outputs that are already in the UTXO set, an RPC error code of -27 with the message "Transaction already in block chain" was returned in response. The error message has been changed to "Transaction outputs already in utxo set" to more accurately describe the source of the issue. (#30212)

• The default mode for the estimatesmartfee RPC has been updated from conservative to economical, which is expected to reduce over-estimation for many users, particularly if Replace-by-Fee is an option. For users that require high confidence in their fee estimates at the cost of potentially over-estimating, the conservative mode remains available. (#30275)

• RPC scantxoutset now returns 2 new fields in the "unspents" JSON array: blockhash and confirmations. See the scantxoutset help for details. (#30515)

• RPC submitpackage now allows 2 new arguments to be passed: maxfeerate and maxburnamount. See the subtmitpackage help for details. (#28950)

Changes to wallet-related RPCs can be found in the Wallet section below.

Updated REST APIs

• Parameter validation for /rest/getutxos has been improved by rejecting truncated or overly large txids and malformed outpoint indices via raising an HTTP_BAD_REQUEST "Parse error". These requests were previously handled silently. (#30482, #30444)

Build System

• GCC 11.1 or later, or Clang 16.0 or later, are now required to compile Bitcoin Core. (#29091, #30263)

• The minimum required glibc to run Bitcoin Core is now 2.31. This means that RHEL 8 and Ubuntu 18.04 (Bionic) are no-longer supported. (#29987)

• --enable-lcov-branch-coverage has been removed, given incompatibilities between lcov version 1 & 2. LCOV_OPTS should be used to set any options instead. (#30192)

Updated Settings

• When running with -alertnotify, an alert can now be raised multiple times instead of just once. Previously, it was only raised when unknown new consensus rules were activated. Its scope has now been increased to include all kernel warnings. Specifically, alerts will now also be raised when an invalid chain with a large amount of work has been detected. Additional warnings may be added in the future. (#30058)

Changes to GUI or wallet related settings can be found in the GUI or Wallet section below.

Wallet

• The wallet now detects when wallet transactions conflict with the mempool. Mempool-conflicting transactions can be seen in the "mempoolconflicts" field of gettransaction. The inputs of mempool-conflicted transactions can now be respent without manually abandoning the transactions when the parent transaction is dropped from the mempool, which can cause wallet balances to appear higher. (#27307)

• A new max_tx_weight option has been added to the RPCs fundrawtransaction, walletcreatefundedpsbt, and send. It specifies the maximum transaction weight. If the limit is exceeded during funding, the transaction will not be built. The default value is 4,000,000 WU. (#29523)

• A new createwalletdescriptor RPC allows users to add new automatically generated descriptors to their wallet. This can be used to upgrade wallets created prior to the introduction of a new standard descriptor, such as taproot. (#29130)

• A new RPC gethdkeys lists all of the BIP32 HD keys in use by all of the descriptors in the wallet. These keys can be used in conjunction with createwalletdescriptor to create and add single key descriptors to the wallet for a particular key that the wallet already knows. (#29130)

• The sendall RPC can now spend unconfirmed change and will include additional fees as necessary for the resulting transaction to bump the unconfirmed transactions' feerates to the specified feerate. (#28979)

• In RPC bumpfee, if a fee_rate is specified, the feerate is no longer restricted to following the wallet's incremental feerate of 5 sat/vb. The feerate must still be at least the sum of the original fee and the mempool's incremental feerate. (#27969)

GUI Changes

• The "Migrate Wallet" menu allows users to migrate any legacy wallet in their wallet directory, regardless of the wallets loaded. (gui#824)

• The "Information" window now displays the maximum mempool size along with the mempool usage. (gui#825)

Low-level Changes

Tests

• The BIP94 timewarp attack mitigation is now active on the regtest network. (#30681)

• A new -testdatadir option has been added to test_bitcoin to allow specifying the location of unit test data directories. (#26564)

Blockstorage

• Block files are now XOR'd by default with a key stored in the blocksdir. Previous releases of Bitcoin Core or previous external software will not be able to read the blocksdir with a non-zero XOR-key. Refer to the -blocksxor help for more details. (#28052)

Chainstate

• The chainstate database flushes that occur when blocks are pruned will no longer empty the database cache. The cache will remain populated longer, which significantly reduces the time for initial block download to complete. (#28280)

Dependencies

• The dependency on Boost.Process has been replaced with cpp-subprocess, which is contained in source. Builders will no longer need Boost.Process to build with external signer support. (#28981)

Credits

Thanks to everyone who directly contributed to this release:

• 0xb10c
• Alfonso Roman Zubeldia
• Andrew Toth
• AngusP
• Anthony Towns
• Antoine Poinsot
• Anton A
• Ava Chow
• Ayush Singh
• Ben Westgate
• Brandon Odiwuor
• brunoerg
• bstin
• Charlie
• Christopher Bergqvist
• Cory Fields
• crazeteam
• Daniela Brozzoni
• David Gumberg
• dergoegge
• Edil Medeiros
• Epic Curious
• Fabian Jahr
• fanquake
• furszy
• glozow
• Greg Sanders
• hanmz
• Hennadii Stepanov
• Hernan Marino
• Hodlinator
• ishaanam
• ismaelsadeeq
• Jadi
• Jon Atack
• josibake
• jrakibi
• kevkevin
• kevkevinpal
• Konstantin Akimov
• laanwj
• Larry Ruane
• Lőrinc
• Luis Schwab
• Luke Dashjr
• MarcoFalke
• marcofleon
• Marnix
• Martin Saposnic
• Martin Zumsande
• Matt Corallo
• Matthew Zipkin
• Matt Whitlock
• Max Edwards
• Michael Dietz
• Murch
• nanlour
• pablomartin4btc
• Peter Todd
• Pieter Wuille
• @RandyMcMillan
• RoboSchmied
• Roman Zeyde
• Ryan Ofsky
• Sebastian Falbesoner
• Sergi Delgado Segura
• Sjors Provoost
• spicyzboss
• StevenMia
• stickies-v
• stratospher
• Suhas Daftuar
• sunerok
• tdb3
• TheCharlatan
• umiumi
• Vasil Dimov
• virtu
• willcl-ark

As well as to everyone that helped with translations on Transifex.