London Hard Fork

London Hard Fork

With Berlin's hard fork already on the mainnet since April 15th, all the focus has shifted towards the next upgrades to the network and what do they bring.

For you people not knowing what is a hard fork, here’s a quick explainer.

A “fork” is a change to the blockchain software that creates two separate versions of the blockchain with a shared history. Forks can be a temporary or permanent split in the network, creating two different versions of the blockchain. Such a permanent split is called Hard Fork.

Hard forks often happen when drastic changes to software validating blocks where old software sees new blocks produced by the latest version as invalid. In Ethereum, when new EIPs are chosen to be included in the “software upgrade”, we can expect for a hard fork to happen. Ethereum Core Devs decides which EIPs are essential to include and batch them together, so no single EIP is added in a hard fork.

We already know the core focus of the London hard fork will be EIP-1559 which we already covered in “New brave world after EIP-1559”. This is a drastic change in how Ethereum will operate, thus requiring a hard fork.

Now we will dig a bit deeper and unravel what the British are bringing!

London baby!

London is scheduled for a release in July this year. We know for sure that 3 EIPs will be included.

  1. EIP-1559
  2. EIP-3238
  3. EIP-3198

We won’t talk about the first one (shameless plug for one of my previous articles). We will focus on the 2nd and 3rd.

EIP-3238 (it’s hard to think of an interesting or funny headline for EIPs…)

To understand this EIP, we need first to talk about Ethereum’s difficulty bomb. It’s part of Ethereum that raises the difficulty of a Proof of Work on Ethereum. Miner’s will get a lower rate of ETH as block times increases. This will lead to the exponential growth of mining difficulty over time, leading to the “Ethereum Ice Age”. During this time, Ethereum will transition from PoW to PoS.
Difficulty Bomb was introduced to deterrent miners from using PoW after Proof of Stake is available.

The bomb will be postponed to mid-2022 with this EIP, giving more time for core developers to switch Ethereum to PoS.


This is related to the EIP-1559 as it adds a new opcode that gives the EVM access to the block’s BASEFEE introduced in EIP-1559.

As we can read in the EIP motivation itself:

The intended use case would be for contracts to get the value of the base fee

This also has more impact, but I encourage you to read the linked motivation in EIP.

In the next post, I will cover Shanghai Hard Fork, the one happening after London. It’s not yet fully defined what it will include, but contemporary pieces of information will give us an overview of what we can expect.