release-notes-27.0.md raw

Bitcoin Core version 27.0 is now available from:

<https://bitcoincore.org/bin/bitcoin-core-27.0/>

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.

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 ===============

libbitcoinconsensus

existed for nearly 10 years with very little known uptake or impact. It has become a maintenance burden.

The underlying functionality does not change between versions, so any users of the library can continue to use the final release indefinitely, with the understanding that Taproot is its final consensus update.

In the future, libbitcoinkernel will provide a much more useful API that is aware of the UTXO set, and therefore be able to fully validate transactions and blocks. (#29189)

mempool.dat compatibility

be written in a new format. This new format includes the XOR'ing of transaction contents to mitigate issues where external programs (such as anti-virus) attempt to interpret and potentially modify the file.

This new format can not be read by previous software releases. To allow for a downgrade, a temporary setting -persistmempoolv1 has been added to fall back to the legacy format. (#28207)

P2P and network changes

by running with -v2transport=0. (#29347)

now follow -v2transport to connect with v2 by default. They will retry with v1 on failure. (#29058)

with (unadjusted) system time. The warning for a large median time offset (70 minutes or more) is kept. This removes the implicit security assumption of requiring an honest majority of outbound peers, and increases the importance of the node operator ensuring their system time is (and stays) correct to not fall out of consensus with the network. (#28956)

Mempool Policy Changes

(aka v3 transaction policy) is available for use on test networks when -acceptnonstdtxn=1 is set. By setting the transaction version number to 3, TRUC transactions request the application of limits on spending of their unconfirmed outputs. 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. TRUC transactions are currently nonstandard and can only be used on test networks where the standardness rules are relaxed or disabled (e.g. with -acceptnonstdtxn=1). (#28948)

External Signing

once the underlying dependency (Boost Process), has been replaced with a different library. (#28967)

Updated RPCs

It remains possible to specify the transport type manually with the v2transport argument of addnode. (#29239)

Build System

Wallet

large input sets and lower transaction costs at high feerates. CoinGrinder searches for the input set with minimal weight. Solutions found by CoinGrinder will produce a change output. CoinGrinder is only active at elevated feerates (default: 30+ sat/vB, based on -consolidatefeerate×3). (#27877)

from outputs feature is used. (#28994)

involving that descriptor, the birth time will be reset to the earlier time. (#28920)

Low-level changes =================

Pruning

flush in order to speed up the syncing of such nodes. (#20827)

Init

result in deletion of files in use by an existing instance. (#28784, #28946)

Credits =======

Thanks to everyone who directly contributed to this release:

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