A blockchain reorganization (reorg) happens when nodes switch from the chain they were following to a competing branch with more cumulative work. Blocks on the abandoned branch become orphans; their transactions go back to the mempool and are usually mined again in the new branch.
Shallow reorgs are normal
Two miners sometimes find a block at the same height within seconds. For a short time, part of the network follows each block, until the next block settles it. A reorg of depth 1 is routine and harmless. You can see every such case on the orphan blocks page.
Deep reorgs are an attack signal
When a miner or pool with a large share of the hashrate withholds blocks and publishes a longer private branch at once, several blocks are replaced together. On 14 September 2025, an alternate chain replaced 18 Monero blocks, past the ten confirmations most services treat as final. Payments that looked confirmed can be reversed by a reorg that deep.
What it means for confirmations
Monero locks outputs for ten blocks, and most exchanges wait for ten confirmations or more. That is safe against accidental forks, not against a miner who controls a large share of the hashrate. The more concentrated mining is, the more confirmations a large payment deserves.
Watch it live
Our node records every reorg it sees, with its fork point and depth: reorg history. The dashboard draws the chain and its forks in real time.