It sounds alarming the first time you hear it: the network can briefly disagree about which block is the latest. Two miners find a block at nearly the same instant, and for a moment different parts of the network see different tips. This is a normal, self-healing event, and understanding how nodes resolve it explains why you wait for a few confirmations before treating a payment as final.
How a short fork happens
Mining is a race, and occasionally two miners cross the line almost together, each producing a valid block at the same height. Both blocks are legitimate. Nodes near one miner hear about its block first; nodes near the other hear about theirs first. For a brief window, the network has two candidate tips and a small fork exists.
How nodes resolve it
Nodes follow the chain with the most accumulated proof-of-work. The fork breaks as soon as the next block is found on top of one of the two candidates. That branch now has more work behind it, so every node switches to it and abandons the other. The losing block transactions return to the waiting pool to be included later. The whole resolution usually takes a block or two.
What a reorganisation is
- A node that had been following the losing branch rewinds and switches to the heavier one.
- This switch is called a reorganisation, or reorg.
- Short reorgs are routine; deep reorgs of long-settled history effectively never happen.
Why you wait for confirmations
Because a very fresh block can still be displaced by a short fork, a transaction in the newest block is not yet completely settled. Each additional block built on top adds more accumulated work behind it, making it exponentially less likely to be reversed. After a handful of confirmations, the chance of a reorg undoing the transaction is so small that it is treated as final. This is why merchants and exchanges wait rather than acting on a zero-confirmation transaction.
What this means for your node
Your node handles all of this automatically. You do not intervene; you simply observe it following the heaviest valid chain at all times. If you ever see your node briefly disagree with an explorer by a block, then snap back into agreement, you have just watched a short fork resolve in real time.
The reassuring takeaway
Forks are not bugs and reorgs are not failures. They are the visible mechanics of a decentralised network converging on one history without a central referee. The waiting period for confirmations is not a flaw to be impatient about; it is the system honestly telling you how settled a transaction really is.