- If you upgrade before the hardfork: You can continue using your existing Bitcoin data directory normally. No blockchain re-download or movement of funds is required.
- If you switch from Bitcoin Core or older Bitcoin Knots after the hardfork: That software may have followed the SHA256d chain. On startup, this release usually notices those extra blocks, walks back to the fork, and then downloads the BLAKE2b chain. That walk-back is only for SHA256d blocks at or after the fork. If a BLAKE2b block itself breaks the data or size rules, run
-reindexto rebuild the database from blocks you already have. Knots versions with the BLAKE2b change will be on bitcoinknots.org when published; source is github.com/bitcoinknots/bitcoin. - A pruned node deletes old blocks to save disk space. If you waited so long that the walk-back blocks are already gone, rebuild the node and download the chain again.
- You do not need to move your bitcoin before the fork. Coins created before the fork remain spendable.
- The first BLAKE2b block includes a short agreed phrase,
blake2b_headline. Set the announced value or your node will reject that block. - After the hardfork, Bitcoin Core and older Bitcoin Knots still require the legacy SHA256d algorithm and follow a different blockchain.
See the release notes for what happened, and the FAQ if you are pruned or unsure which software you are running. Miners using their own templates should read DATUM and Knots.