This hardfork is not BIP-110. BIP-110, in alignment with the vast majority of node policy, was a softfork, later rejected, that would have rejected use of the network for arbitrary data storage. A hardfork is a break away from abuse of the Bitcoin network. This hardfork changes proof of work from the legacy SHA256d algorithm to the stronger and quantum-resistant BLAKE2b algorithm, so today's SHA256d miners cannot produce valid blocks here.
Limits on arbitrary data storage start at that same height as a flag day, not a leftover versionbits vote, and apply to v2-header blocks until the previous block's median time past reaches 1 September 2027, 00:00 UTC. During that window, blocks are also limited to 700,000 weight units, about 300 kB of typical payments. Inputs that spend coins created before the fork are exempt from the new script and data rules.
Each BLAKE2b block uses a 164-byte header v2, not the classic 80-byte SHA256d header. Light-client protocols that hash an 80-byte header with SHA256d will not validate this chain until they learn the new format and BLAKE2b.
Integration checklist
- Use a BLAKE2b node, not Bitcoin Core or a pre-hardfork Bitcoin Knots release, if you intend to follow this chain. Source: bitcoinknots/bitcoin.
- Set the announced
blake2b_headline. A node with a different value will not accept the first BLAKE2b block. - If a node followed post-fork SHA256d blocks, this release usually walks back to the fork and downloads the BLAKE2b chain. That pass uses headers only. A BLAKE2b-era block that breaks the weight cap, output sizes, or script rules still needs
-reindex. A pruned node that has already deleted the walk-back blocks must resync. - After the previous block's median time past reaches 1 September 2027, 00:00 UTC, the data limits and the weight cap are removed unless node operators later choose to continue them. BLAKE2b proof of work is not temporary.
getdeploymentinforeportsreduced_dataas a flag-day deployment.getblocktemplatelists it inrulesonly while the window is open. There is no miner signaling bit.
Miners constructing their own templates should use the DATUM Gateway with Knots. See miners and DATUM.
The proof-of-work change is specified in Knots PR 359. The reduced-data flag day and MTP expiry ride that height in PR 358.
Read the release notes, node operator guide, and FAQ.