When miners find conflicting blocks that each build on the same chaintip, two or more competing chaintips emerge. At a certain point, a miner will discover a new block that results in a clear elongation of one of the competing chaintips beyond the others resulting in the emergence of a clear longest proof of work chain.

At this point, any miner working on a shorter chaintip will cease trying to build on the failed extension and migrate their work to the longest tip. Part of this process is the removal of transactions from the now defunct blocks and the construction and validation of the Merkle tree for the blocks in the new longest chaintip.

This is called a re-org as it is the re-organisation of all transactions in the now orphaned chaintip to match the ordering of the new longest proof of work chain.

These are common events (approximately one in every 300 blocks results in a race) and are an important part of the Nakamoto Consensus mechanism.

« Back to Glossary Index

Written by Ramon Quesada

Passionate about Blockchain & Bitcoin technology since 2013, Co- Founder of, Team Manager in the CoinTelegraph Spain franchise (2016-2017 years) Co. Organizer of the Blockchain Boot camp Valencia 2018, Co. Organizer of the mini Hackathon BitcoinSV Barcelona, in August 2019, current coordinator of the BSV Valencia Meetup.