The most disputed change in v30 is a policy update around OP_RETURN—the script path used for provably unspendable outputs that can carry arbitrary data. Bitcoin Core has raised the default -datacarriersize limit to 100,000 bytes and now permits multiple data-carrier (OP_RETURN) outputs in a single transaction for relay and mining. Crucially, node operators can still restore the previous behavior: “It can be overridden with -datacarriersize=83 to revert to the limit enforced in previous versions.” The aggregate size limit applies across all OP_RETURN outputs in a transaction.
Beyond OP_RETURN, v30 delivers a long list of network, wallet, and tooling updates. The P2P layer improves package relay so that common topologies like grandparent-parent-child or multi-parent-one-child can propagate more reliably when only one ancestor needs fee bumping. The transaction orphanage introduces stronger DoS limits based on total entries and weight across peers, replacing the now-retired -maxorphantx knob.
Miners gain an experimental IPC mining interface accessible through a new umbrella bitcoin command that also provides convenience aliases—“bitcoin node,” “bitcoin gui,” and “bitcoin rpc”—without deprecating existing binaries. External signing on Windows is re-enabled, and the coinstats index has been reworked to avoid an overflow bug seen on default Signet, requiring a one-time resync of that index.
Fee-policy defaults also shift. The minimum block feerate setting (-blockmintxfee) now defaults to 0.001 sat/vB, while both the minimum relay and incremental relay feerates default to 0.1 sat/vB. The notes stress that unless these lower defaults are broadly adopted, propagation and confirmation are not guaranteed; wallet feerates themselves are unchanged without explicit configuration.
At press time, BTC traded at $114,455.
