A consensus mechanism is the way a blockchain gets all the nodesNodeA computer that runs a crypto network's software, keeps a copy of the blockchain and checks that new transactions and blocks follow the rules. on its network to agree on one shared history. It answers two questions: who gets to add the next block, and which version of the chain counts if two compete.
Why is it needed?
A bank keeps one set of books and decides what is correct. An open blockchain has thousands of computers and nobody in charge. Some participants might want to cheat, for example by spending the same coins twice, which is known as double spendingDouble spendingSpending the same digital money twice; the problem Bitcoin was the first system to solve without a bank or other middleman..
A simple vote, with one vote per computer, doesn't work. Satoshi Nakamoto pointed this out in the Bitcoin whitepaper: anyone able to get hold of many IP addresses could vote many times. The solution is to make each vote cost something that can't be faked.
The most common methods
- Proof of workProof of workA consensus method where the right to add the next block to a blockchain goes to whoever first solves a hard computing puzzle.. Votes cost computing work and electricity. Miners compete to solve a puzzle, and the chain with the most work behind it counts. Bitcoin uses this method.
- Proof of stakeProof of stakeA consensus method where crypto is locked up as a stake for the right to create blocks, and anyone who cheats can lose part of that stake.. Votes cost crypto locked up as a stake. ValidatorsValidatorA participant on a proof-of-stake network who locks up their own crypto as a stake to create and check blocks in return for rewards. who cheat can lose their stake. Ethereum has used this method since 15 September 2022.
- Proof of authority. A few known parties that have been given permission confirm the blocks. This method is mostly used in private networks and test networks.
What to keep in mind
No consensus mechanism is perfectly secure. If one party gains a majority of the computing power or the stake, it can carry out a 51% attack51% attackAn attack where one party controls more than half of a network's computing power or stake and can then rewrite recent transactions.. On large networks such as Bitcoin and Ethereum that is extremely expensive, and that is exactly the point. Cheating should cost more than it gains.
Everything in Myntkaup Learn is written and regularly reviewed by the Myntkaup editorial team. It is for education and is not investment advice. Editorial policy. Updated 18 October 2026.