August 12, 2021

History Of Ethereum Hard Forks

Okereke Innocent


Before the Ethereum Blockchain could reach its potential, it needed several transformations. Such transformations include migrating to Ethereum 2.0 also known as Serenity. ETH 2.0 is the much-awaited Ethereum upgrade that allows a more scalable, cheaper, decentralized, and secure network.

Ethereum has since chanted the course to migrating from the POW to POS consensus for cheaper transaction costs and better decentralization. Accompanying the upgrades are various hard forks promising various Ethereum Implementation Proposals, EIPs.

By the way, what is a fork, and what exactly is a hard fork? The fork is the process of copying and improving on an existing protocol, similar to the traditional software upgrades.

A fork can be soft, hard, accident, and intentional. It is a hard fork when it changes the rules of the blockchain protocol so that the old blockchain and the resulting blockchain are incompatible.

A hard fork is a radical upgrade that can make previous transactions and blocks either valid or invalid and requires all validators in a network to upgrade to a newer version. It’s not backward-compatible. A soft fork is an upgrade to the software that is backward-compatible and has validators in an older version of the chain that sees the new version as valid.

When two or more miners find a block at the same time, an accidental fork occurs but it is intentional when the rules of the network are being modified.

Ethereum Hard Fork And Others

Similar to other blockchain networks with active communities, Ethereum Blockchain has undergone soft and hard forks over time. For a brief, we need to reference other non-Ethereum hard forks before explaining Ethereum hard forks in detail.

So far, Bitcoin, the first implementation of blockchain launched by Satoshi Nakamoto, a pseudo-anonymous entity, has also undergone several hard forks. The most prominent Bitcoin hard forks are; Bitcoin XT, Bitcoin Classic, Bitcoin Unlimited, Segregated Witness (SegWit), Bitcoin Cash, and many others. From records, one common thing about the various hard forks, both Ethereum and Bitcoin hard fork, is that they are geared towards protocol upgrades which are done by network consensus. 

Why Fork Ethereum Blockchain?

Similar to other network and software upgrades, Ethereum concerns birthed the various hard forks. It ranges from security, centralization, fees, scalability, and other Eth 1.0 limitations. For instance, despite having a good run in Q1 and Q2 2021, Ethereum had its highest fees that scare developers. A simple swap on the Uniswap for example is as high as $100 while others could be $16-20. 

While we are set to discuss Ethereum Hard forks fully, it is important to note the Ethereum journey so far and link them to the hard forks accordingly. The journey as referred to here is the Ethereum developmental roadmap. 

Ethereum Developmental Upgrade And Associated Hard Forks

Ethereum has a four-stage development roadmap. They include; frontier, Homestead, Metropolis, and Serenity. Recall that, unlike most POW networks, Ethereum is way beyond currency and has to measure up to accommodate varying use cases and features. Hence, the need for a roadmap. 

Below explains the various journey so far; 


The frontier is the first developmental roadmap of the Ethereum blockchain. It went live on July 30, 2015. Although it went live as a beta, it performed better than expectations. Developers began writing smart contracts and decentralized applications to deploy on the Ethereum Blockchain. Shortly after its launch, it experienced a hard fork called Ice Age. 

Ice Age, also known as “Frontier Thawing”, was the first (unplanned) fork of the Ethereum blockchain aimed at providing security and speed updates to the network.


While the Frontier phase of Ethereum laid the groundwork for experimenting in Ethereum, the Homestead steps it up to its first production release. Homestead, the second major version of the Ethereum release, comes with several protocol changes and a networking change that provides the ability to do further network upgrades. 

The upgrades changes was activated at Block >= 1,150,000 on Mainnet

Block >= 494,000 on Morden

Block >= 0 on future testnets. The homestead hard forks include:

EIP-2: Main homestead hard fork changes

EIP-7: Hard fork EVM update. DELEGATECALL

EIP-8: devp2p forward compatibility. 

Ethereum Classic Hard Fork

The Ethereum Classic hard fork is a child of necessity after the homestead hard fork. It was in 2016 when hackers exploited DAO, one of the most notable Ethereum projects. As a result, developers initiated the Ethereum Classic hard fork to mitigate the DAO loss. 

The DAO, also called Distributed Autonomous Organization, raised $150m in Ether in a public crowd sale. 

The DAO, in principle, was to operate as a form of decentralized venture capital fund where investors would send Ether to the DAO to receive voting rights, whereafter those who had invested (and voted) would democratically decide on which projects to which the DAO should disperse those funds.

Contrary to the arrangement, the DAO was unable to complete its vision when millions of Ether vanished.

As a response, the Ethereum community moved to recover the funds by voting to change Ethereum’s baseline code to recover the lost funds and reimburse investors. As a result of the majority vote in the favor of this proposal, a hard fork and two separate blockchains were created. 

EtherZero Hard Fork

EtherZero is the second intentional Ethereum hard fork that took place in 2018. The hard fork went live at 4936270 block on 29 Jan 2018. Unlike the Ethereum Classic hard Fork, it was started by a group of tech geeks looking to provide a better platform for creating decentralized applications (dApps) and smart contract deployment. Contrary to other forks, it has no specific interest to speed up transaction rates. Rather, the development team was determined to make transactions completely free.


This is the third phase of the Ethereum upgrade and one of the notable hard forks. It is the forerunner to Serenity in the sense that it lays the background for early proof of stake (POS). Metropolis upgrade includes Byzantium, Constantinople, and early serenity. Byzantium is a backward-compatible upgrade aimed at integrating zero-knowledge protocol and delay of the network difficulty bomb. On the other hand, Constantinople is a non-backward compatible upgrade.

It represents a hard fork deployed to solve a security weakness allowing hackers to access users' funds and integrates a smart contract functionality that enhances the verification process as well as the reduction of gas price. Lastly, as a forerunner to serenity, it made the first attempt of implementing POS and account abstraction.


Also known as the Ethereum 2.0, serenity is the latest Ethereum upgrade. It builds and improves on the successes of the previous upgrades and hard forks. The major improvement of the Serenity upgrade is porting from POW to POS fully. 

By implication, serenity increases its transaction capacity, changing gas fees and achieving scalability while achieving more eco-friendly coin generating and validating networks. 

The launch of the Beacon chain is Serenity's first step to revolutionizing the Ethereum network. From the Beacon chain, it pushes through to; Berin hard fork, London hard fork, and the upcoming Shanghai hard fork. 

Berlin Hard Fork

The Berlin hard fork is a forerunner to the London hard fork. It is named after the host city of the inaugural Ethereum Devcon convention. Berlin hard fork incorporates several EIPs which addresses gas price and introduces new transaction types. 

The Berlin hard fork went live at 12,244,000 on April 15 and proposes several EIPs. The EIPs include; EIP 2565, EIP 2718, EIP 2929 and EIP 2930. 

Before the Berlin hard fork went live, several delays were citing possible vulnerabilities and centralization concerns. Some believed the Berlin hard fork will be less impactful in the short term, but will further pave the way for the upcoming London hard fork. 

London Hard Fork

After the Berlin Hard Fork comes London hard fork, scheduled for July before being delayed to August 4. In preparation for the ETH 2.0 launch in 2022, London hard fork makes significant changes to Ethereum’s transaction fee system, which has long been a contentious subject.

Ethereum's London hard fork introduces two new known Ethereum Improvement Proposals (EIP), namely: EIP-1559 and EIP-3238. EIP-1559 is a proposed change to the way users pay gas fees on the Ethereum network. It also proposes a new transaction pricing mechanism that will create a base fee for each block. Usually, users enter a bid to pay their gas fees, but the EIP-1559 allows miners to prioritize transactions based on the fee added and use the fee as a reward for adding it to a block. Now, each block will have a fixed, associated fee instead. The EIP design allows the blockchain to burn the fee, reducing the overall supply of Ether (ETH). Thereby creating deflationary pressure on the cryptocurrency.

Ethereum 1.0 has a difficulty in mining called the difficulty time bomb. As miners reach the difficulty time bomb, it takes longer to mine a new block, and thus reward gets lower as well as slower transaction. To motivate users and encourage them to move to Ethereum 2.0 upon launch, EIP-3238 will delay the time bomb to enable the network to incentivize validators to Ethereum 2.0’s Proof of Stake consensus model at the correct time. It is suspected that if there is no consensus to move to the awaiting Ethereum 2.0, the scenario of Ethereum Classic will happen. Delaying the time bomb will lead to a 30-second block time ice age around Q2 of 2022, therefore, enabling "The merging" of Ethereum 1.0 with Ethereum 2.0.

Shanghai Hard Fork

The upgrade didn't stop at Berlin and London hard Fork. It proceeded to the Shanghai hard fork scheduled for OCTOBER 2021. Shanghai hard fork is promised to include the following EIPs; 

  • EIP-3074: This EIP introduces two EVM instructions AUTH and AUTHCALL that bellows for sponsored transactions. The EVM instructions AUTH sets a context variable authorized based on an ECDSA signature while the AUTHCALL sends a call as the authorized that delegates control of the EOA to smart contract.
  • EIP-2537: This EIP adds the BLS-12381 curve, used by the beacon chain, and will finally be good support for the ETH2.0 transition period.
  • EIP-2327:It introduces a new opcode and Opcode BEGINDATA for Solidity devs and Optimism teams.

The new opcode BEGINDATA indicates that the remaining bytes of the contract should be regarded as data rather than contract code and cannot be executed.

  • EIP-2935: This EIP would be helpful to light clients.


Ethereum Blockchain so far has been a work in progress. It started from a four developmental roadmap Viz: frontier, homestead, metropolis, and serenity to achieve what we will call ETH 2.0 2022. Every upgrade of Ethereum accompanied an associated hard fork. The major Ethereum hard forks are Ethereum Classic, Shanghai, London, Berlin, Homestead, Constantinople, and Ice Age hard forks. It is expected that the Ethereum network will attain scalability with eco-friendly network fees and better decentralization. The ETH 2.0 is promised to provide a sustainable blockchain network that doesn't compromise any of the above features. 


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