Version bits FAQ for miners Author: Bitcoin Core Last Updated: 18 April 2017 Overview What is version bits BIP9? How is version bits activated? What are soft fork timeouts? What is the activation workflow? What is the version bit? When should miners set bits? How does it differ to an ISM soft fork? Do miners have to upgrade? Who assigns version bits to different upgrade proposals? Further reading What is version bits BIP9? The version bits BIP9 system is a way to introduce backward compatible rule changes to the Bitcoin consensus rules, known as a soft fork. version bits allows miners to signal that they can validate the soft fork rules. It also allows for up to 29 soft forks to be proposed concurrently. How is version bits activated? version bits does not require activation, it’s simply a way for miners to signal readiness for a soft fork by setting bits in the block header nVersion field. What are soft fork timeouts? Soft forks have a start time and an timeout during which the proposal is active. The soft fork can only be activated between start time and timeout. If the soft fork does not get activated by the timeout, the
