Hard forks and other upgrades: a brief history of Ethereum

A brief description of the significant milestones of the Ethereum cryptocurrency and its planned future roadmap.

An overview of the upgrades and hard forks of Ethereum’s past, with an eye towards what lies ahead.

Throughout its existence, Ethereum has been subjected to six “hard updates, which have led to significant changes in its blockchain. These events are called hard forks and are in fact branches of the network, where all users have to switch to a new improved version of the software. This is how it happened to each of the pre-conceived updates. But there were also unscheduled hard forks of Ethereum, which were carried out because of the hacker attacks. Let’s look at the Ethereum history more closely.

The Beginning

Originally launched on July 30, 2015, the Ethereum blockchain platform worked as an early alpha version called Frontier. Due to the instability and inconvenient way of interacting with the network (through the command line), this period was also called the “Wild West”, hinting at the huge potential of the new network, which is inextricably linked to equally huge risks.

Frontier was the first viable version of the Ethereum blockchain, at the time not so much for the end-user as for the “first settlers” — enthusiast developers who got the tools to mine, create dApps and conduct various experiments on the network. When most of the bugs in the platform code were fixed and adapted to the average user, a new milestone began. On March 14, 2016, the first of the planned Ethereum hard forks, Homestead, was implemented on block 1,150,000.

An important element of this upgrade was the elimination of the so-called “canary contracts”, which gave the Ethereum development team the opportunity to undo user actions on the network. This was the first step towards moving the Ethereum blockchain to a more decentralized state.

Also, the following updates were implemented:

  • The fee for the creation of smart contracts through a transaction was changed (from 21,000 to 53,000 gas);
  • The mechanism for calculating the complexity of Ethereum mining was adjusted;
  • Added support for the DELEGATECALL command, allowing developers to overcome the gas limit problem in the block;
  • Network compatibility with future protocol changes has been improved;
  • The maximum value of s-value in the transaction signature is limited in order to protect against spam.

Also, thanks to the release of the official Mist wallet, ordinary users were finally able to interact with the network through a user-friendly interface. It was about storing and sending coins as well as working with smart contracts.

This protocol update brought blockchain to a stable state, which allowed many projects to start using it actively. However, Ethereum had its first serious trouble ahead.

Ethereum Classic

On June 16, 2016, unknown hackers attacked the DAO (Decentralized Autonomous Organization) project, a crowdfunding platform based on Ethereum smart contracts, which was introduced as a fundamentally new model of financial management and investment. The attack became possible because of the developers’ ignoring the vulnerability in the code of the smart contract, which was eventually used by the attackers, stealing a third of the funds raised from investors (about $ 50 million in ETH).

In the following weeks, developers, miners and other members of the Ethereum community actively discussed the possibility of recovering stolen assets by network rollback to the state that was before hacking.

On July 20, the developers’ idea was implemented on Block 1,920,000 in the form of a controversial Ethereum hard fork, which returned investors’ funds but was not supported by the followers of the idea of decentralization, based on the inadmissibility of such an intervention in blockchain. As a result, the old network chain continued to exist in the form of the Ethereum Classic project with its own development team.


In October 2016, the network was subjected to several DoS-attacks on spamming and empty transactions, which were responded to by two more unscheduled hard forks:

  1. EIP-150 (Block 2,463,000 on 18 October) was an urgent technical effort to improve network resilience;
  2. Spurious Dragon (November 22 on Block 2,675,000) — consisted of several updates aimed at changing the maximum size and pricing of operating codes, making future possible attacks financially unprofitable for hackers. It also implemented protection against replay attacks and a mechanism to remove blank accounts created by hackers, which helped reduce the size of blockchain and speed up client synchronization.

3. Judging by the fact that Ethereum network was not slowed down anymore due to intentional actions of hackers, Ethereum hard forks were effective.

Metropolis and Byzantium

The next planned phase of development was Metropolis — a set of updates to prepare the network for the transition to the Proof-of-Stake (PoS) mining algorithm and the implementation of solutions for network scaling, which due to the complexity of simultaneous implementation of all planned changes was divided into two separate hard forks.

The Byzantium upgrade was activated on 16 October 2017 at Block 4,370,000 and focused on optimizing gas consumption, improving safety and speed of the network. An important element was the transfer of the almost activated complexity bomb by a year and a half ahead. This is one of the reasons why hard fork was carried out on that date — further growth in the complexity of the network would have led to the termination of mining and the onset of the “ice age”, to which the Ethereum was not yet ready.

Support for verification of RSA signatures, several new operating codes and cryptographic models, as well as the use of smart contracts in confidential transactions using zk-SNARKs tools were also added. In addition, Byzantium has implemented a parallel transaction chain processing mechanism that should help develop future blockchain scalability and significant acceleration solutions.


The second update of the Metropolis phase was initially expected to be implemented on November 2018. However, after an attempt to launch Constantinople hard fork in the test network, the project team faced a number of critical bugs that disrupted the network.

It was then announced that the Ethereum hard fork will be held on January 17th at Block 7,080,000. But just a day before the activation, Constantinople was cancelled again. The reason for this was the discovery of a vulnerability in one of the included updates (EIP 1283) that could have been exploited by the attackers to carry out a “re-entry attack” and steal users’ funds.

There was no time to fix the problem update because of the urgent need to migrate the bombs again, which did not start to work in time. Therefore, EIP 1283 was simply decided to remove from the planned network upgrade assigned to block 7 280,000, which was supposed to be found in the last days of February.

Constantinople was activated on the night of February 28 to March 1. Together with it, the updating of St.Petersburg which has removed from a bad network EIP has been started. Activation of this update led to another delay of the “complexity bomb” (by about 12 months), a reduction in the miner award (from 3 ETH to 2 ETH) and the time of extraction of the block to a record 13 seconds (before that was 20–21 seconds).

In addition, the gas requirements for some types of transactions were reduced, the efficiency and speed of the Ethereum virtual machine were improved, and the smart contract code was optimized and the ease of development was improved.

The future and perspectives of Ethereum

The activation of Constantinople has prepared the Ethereum network for the last of the planned stages of the complex updates under the general name of Serenity. Its implementation should lead to the transition to Casper PoS protocol and the cancellation of the current mining model.

Also, developers work on sharding, a technology that will help scale Ethereum by implementing a mechanism for processing transactions by multiple parallel blockchains connected to a common network. When both solutions are implemented, this will a new era of Ethereum 2.0, an energy-efficient blockchain platform capable of handling thousands of transactions per second.

According to the latest data, the Ethereum Roadmap now includes the launch of Beacon Chain (the Casper protocol management solution) in early 2020, the implementation of the remaining components of Serenity in the fall of the same year, and yet unnamed Ethereum hard fork in 2019, which will reduce coin emissions by a factor of 10 in March 2021.

It is safe to say that the productive work of the developers from Ethereum Foundation will have a positive impact on the price of cryptocurrency. Its network is the second most popular after Bitcoin, so Ethereum price prediction for 2019 is quite exciting.

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Blockchain enthusiast developer and writer. I love video games, blockchain and the hot symbiosis of these two worlds.