> ## Documentation Index
> Fetch the complete documentation index at: https://docs.theblockchainlibrary.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Chain Reorganization

> A change in canonical blockchain history when one recent branch is replaced by another branch accepted by consensus.

# Chain Reorganization

A change in canonical blockchain history when one recent branch is replaced by another branch accepted by consensus.

## Definition

A change in canonical blockchain history when one recent branch is replaced by another branch accepted by consensus.

## Why it matters

Consensus concepts explain how independent nodes agree on one shared history without a central coordinator.

## How it works

Nodes constantly listen for the branch with the most work. When a node detects a longer chain, it updates its local pointer to the tip of that chain. It then discards the blocks it previously validated that are not part of this new, longer path.

## Real-world example

Ethereum experienced a 'deep' reorg during the transition to Proof of Stake, where nodes briefly disagreed on the chain tip before consensus was restored.

## Advantages

* Allows the network to resolve disputes automatically
* Maintains consensus even with temporary network delays
* Ensures the network eventually aligns on one truth

## Limitations

* Can cause transaction rollbacks for users
* Introduces uncertainty into transaction finality
* Potentially exploitable for double-spend attacks

## Common misconceptions

* Many think a reorg is a sign of a hack, but it is a normal part of distributed consensus.
* Some people believe reorgs are permanent, but they are resolved automatically by the protocol.

## Related knowledge

* [Block Producer](/generated/v2/glossary/block-producer) — term
* [Finality](/generated/v2/glossary/finality) — term
* [Proof of Stake](/generated/v2/books/proof-of-stake) — term
* [Validator](/generated/v2/glossary/validator) — term

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**Canonical knowledge ID:** `glossary:chain-reorganization`