Choosing a blockchain fork in Bitcoin Core According to this, the BIP 148 UASF (user activated soft fork) goes into effect on August 1. Supposing it results in a substantial fork in the blockchain, is there a way users of Bitcoin Core can choose which chain to use (as opposed to whichever chain one's node receives first)? In other words: How do I tell Bitcoin Core to use an alternative chain?

Is this what preciousblock* is for?

*"Treats a block as if it were received before others with the same work."
From what you linked it seems to me that preciousblock doesn't supersede a longer chain, it just prioritizes one block over another at the same height.

You could call bitcoin-cli invalidateblock &lt;blockhash&gt; on the first block of the chain that you wish not to follow.