Immutability of blockchain transactions simply explained

There is too much noise in blockchain-related news on the Internet. The cleaner the content, it is often too technical. Of course, source code is the purest and most reliable content. But even without plunging into the depths of technical truths, in the early stages of experiencing the industry, you will always run into new meanings and terms when mastering new material. Today we will take a closer look at immutability (or irreversibility), which is closely related to one of the main characteristics of Blockchain technology — reliability.

What is immutability?

It has a lot to do with confirmations, but it’s not that simple.

Why is immutability essential?

After an hour of waiting, it becomes obvious that a short time of completion is extremely important for a business. You do not want to wait 10 minutes every time you go shopping in a new store. Just imagine how long it would take to send money to a friend? The financial sector will never be able to meet the clients’ speed expectations as traditional transactions are completed in less than a second (how final they are is a different question).

How does it work?

Depending on the design of the protocol, a blockchain achieves immutability through various mechanisms. There are many mixed options, but for general understanding, three main types are most often mentioned:


This type of immutability is complex because there is no such thing as a 100% immutability state in real life. After a transaction is executed in a certain blockchain, other transactions get confirmed and continue to arrive. Thus, theoretically, it is plausible for the miners to switch to an alternate chain, starting with the block previous to the one containing your transaction, making your transaction invalid. But the more transactions occur after yours, the more resources it will take to switch chains, and at some point, it becomes insanely irrational, so the probability of this happening reduces.


This one is clearer.


Economic immutability is based on the idea of staking and penalties, so it mainly applies to PoS protocols. Immutability is achieved when block recovery becomes financially costly. Validators vote for block inclusion or rejection. Consensus conditions vary from blockchain to blockchain, but usually, about 2/3 of validators are enough to approve a block. All validators who vote against the majority are penalized according to the rules of the chain (lose their share, lose the opportunity to get a reward for the next period, and so on). Usually, when we go back in history, the cutoff is multiplied, which makes it more expensive to restore old blocks. You will simply regret making the wrong choice.


Achieving fast and safe immutability is still a rather active area of research for various blockchains. The reversibility of blocks can lead to losses of millions of dollars or affect decentralized applications’ fundamentals. Thus, understanding immutability is crucial when creating reliable blockchain-platforms and selecting the platform for application development.

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