What is Ethereum Hard Fork? Why is Ethereum Hard Fork happening?

By Le Anh | Invest

Ethereum Hard Fork

Ethereum Hard Fork is an event to change the rules and regulations that are being applied on the blockchain Ethereum. It makes the blocks, transactions confirmed by the old rule become invalid.

Ethereum Hard Fork is not like many other blockchains. The hard forks taking place within the Ethereum network are almost planned in advance and the new blockchain will follow the fork chain.

You can look at the image below to understand better:

Ethereum's Hard Fork history


Ethereum's first Hard Fork was held on May 14, 05 at block 2016. It marks the transition of Ethereum's development stage from Frontier to Homestead with three major changes:

  • Removed Canary contract function.
  • Introducing new code in the Solidity programming language.
  • Introducing the Mist wallet, which allows users to hold, transfer ETH, write and deploy smart contracts.

DAO Hard Fork

Ethereum's second hard fork took place by an unexpected event - The DAO Hack.

To get back the hacked money, Ethereum decided to Hard Fork. And the result of this split the Ethereum blockchain into two different chains, Ethereum (ETH) and Ethereum Classic (ETC).

Of course, ETC is the original chain of Ethereum.

Tangerine Whistle

EIP-150 Hard Fork (aka Tangerine Whistle) is Ethereum's third Hard Fork.

It took place at the 2,463,000 block on October 18, 10 with the update of the network gas charges to address the issue of Dos service attack.

Spurious Dragon

Ethereum took place the fourth Hard Fork - Spurious Dragon at block number 2,675,000. Along with the official adoption of new EIPs (EIP-155, EIP-160, EIP-161 and EIP-170) into the Ethereum blockchain.


  • EIP-155: Prevents transactions on the Ethereum blockchain from being replayed on alternative blockchain (testnet).
  • EIP-160: Increase EXP fee according to calculation complexity.
  • EIP-161: Allows deleting a large number of empty accounts to be brought into the state at a very low cost due to previous DoS attacks.
  • EIP-170: Change the maximum code size that contracts on blockchain of Ethereum may have (24,576 bytes).


This is the fifth Hard Fork of Ethereum to take place at block 4,370,000 with the update of 9 EIPs proposals. This is to improve the security, scalability and security attributes of Ethereum.

The EIPs include: EIP-140, EIP-658, EIP-196 & EIP-197, EIP-198, EIP-211, EIP-214, EIP-100, EIP-649.


This is the sixth Hard Fork and also one of the important Hard Fork in the transition PoW consensus mechanism to PoS of Ethereum.

After many delays, January 16, 01 at 2019 Hard Fork Constantinople has been successfully implemented with the update of 7,080,000 EIPs with the following changes:

  • Optimize gas usage (EIP-145, EIP-1052).
  • Enables activation of layer2 solutions such as state channel (EIP-1014).
  • Delay difficulty and reduce block rewards from 3ETH to 2ETH for each block mined (EIP-1234).


This is Ethereum's last Hard Fork to take place at 9,069,000 blocks with updates of six EIPs proposals.

  • EIP-152: Activate compatibility with ZCash and other Equihash-based blockchains.
  • EIP-1108: Reduce gas charges for STARKs and SNARKs.
  • EIP-1344: Addition of an ID system to prevent replay attacks between different blockchains.
  • EIP-1844: Increases the gas cost of some intensive EVM activities to prevent spam attacks and achieve a better gas / resource balance.
  • EIP-2028: Deploying smart contracts zk-SNARK and zk-STARK become cheaper.
  • EIP-2200: Change the way of calculating storage costs in EVM.

Why is Ethereum Hard Fork happening?

Hard Fork takes place to make new changes, add new features to improve the Ethereum network better.

Ethereum's hard forks are all planned in advance according to the roadmap from the early days. So often Hard Fork of Ethereum rarely encountered problems because they prepared very carefully.

Despite a number of hard forks occurring unexpectedly, Ethereum continues to move closer to the transition PoS consensus mechanism mine.

In the future, Ethereum needs two more Hard Fork, Berlin & London to officially complete the transition to PoS.

The impact of Hard Fork on Ethereum

ETH price

The price of ETH barely increases too much every time the Hard Fork takes place, even falling slightly.


All dapps on Ethereum need to keep up to date with the latest software version compatible with the blockchain after Hard Fork.

Otherwise, the smart contract of Dapps will not work on the new block chain.


Every time the Hard Fork happens, Ethereum gets closer to Proof of Stake (PoS). As a result, the miner's position in the Ethereum network is getting weaker.

Because the mining profit is lower than the staking of ETH, making some miners stop mining ETH can have a slight impact on network security in the short term.


Hopefully through this article, you have a better understanding of Ethereum's Hard Fork since its inception.

If you have any questions please comment below this article, I and the Coin98 team will respond as quickly as possible.

Now, goodbye and see you again in the upcoming article!

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