Bitcoin Core 32.0, the open-source program that powers the vast majority of full nodes on the network, tagged its first release candidate on September 14 and is targeting a stable release on October 10.

The update doesn't change Bitcoin's consensus rules. Instead, it focuses on under-the-hood improvements that make running a node faster, cheaper, and less likely to get exploited by a well-crafted attack.

The headline performance improvement in v32.0 comes from a rethinking of how the software validates blocks. Bitcoin Core now fetches transaction inputs in parallel during block validation, rather than processing them sequentially. In testing, this change produced up to 3x faster initial block downloads.

Initial block download, or IBD, is the process a new node goes through to sync with the entire Bitcoin blockchain from scratch. Cutting that time by a factor of three makes it meaningfully easier for new participants to join the network.

Version 32.0 introduces a mempool-based fee estimation mechanism that supplements the historical model. The mempool is essentially the waiting room for unconfirmed transactions. By examining what's currently sitting in the mempool, the software can recommend lower fees during periods of reduced congestion.

Bitcoin Core 32.0 resolves a command-execution vulnerability in the walletnotify feature that has been present since version 24.0 on non-Windows systems.

The update also introduces a memory-exhaustion fix targeting the new web server component.

Four RPC commands now default to PSBT version 2, a change that could break existing integrations if developers aren't prepared for it.

PSBT, or Partially Signed Bitcoin Transactions, is a standard format for passing around unsigned or partially signed transactions between different wallets and signing devices. Version 2 of the PSBT standard offers more flexibility, but applications and services that parse PSBT output from Bitcoin Core will need to update their code to handle the new format.

Wallet developers, exchanges, and custody providers that interact with Bitcoin Core's RPC interface should be testing against the release candidate now rather than scrambling after October 10.