When the chain splits.
WHAT A FORK IS
A divergence in the chain.
WHAT A TEMPORARY FORK IS
Two valid blocks produced nearly simultaneously, resolved as one chain extends.
WHAT A SOFT FORK IS
A rule change that older software still accepts.
WHY THAT MATTERS
It does not require everyone to upgrade.
WHAT A HARD FORK IS
A rule change older software rejects.
WHAT IT REQUIRES
Everyone upgrading, or the network splits permanently.
WHAT A PERMANENT SPLIT PRODUCES
Two networks, each with its own history before the split and separate histories after.
WHAT HOLDERS RECEIVE
Holdings on both, since the pre-split history is shared.
WHY FORKS HAPPEN
Disagreement about direction, which cannot be settled by authority.
WHAT THAT REVEALS
Governance in open networks is social, not technical.
WHAT REPLAY ATTACKS ARE
A transaction valid on both chains being submitted to the other.
WHAT PREVENTS THEM
Replay protection, which responsible forks implement.
WHAT TO DO DURING A FORK
Wait for stability before transacting.
WHY
Exchanges and wallets may suspend activity, and confusion is exploited.
WHAT TO BE CAUTIOUS OF
Claims that a fork provides free value.
