Gavin Wood publishes the Ethereum Yellow Paper, which explains how Ethereum’s virtual machine and consensus rules work at a technical level. This helped turn the project from an idea into a system other developers could implement and review. It also set a baseline for later client software and upgrades.
Ethereum starts the “Olympic” testnet phase to stress-test the network before mainnet. The team uses incentives (prizes) to encourage mining and heavy usage so bugs show up early. This testing phase helped prepare for the first live release.
Ethereum’s first live mainnet release, called Frontier, goes live when participants generate and load the genesis block. Frontier is positioned as an early, command-line-focused release aimed at developers, miners, and exchanges. This marks the start of Ethereum as a running public blockchain for smart contracts.
Only a few months after mainnet launch, the first Devcon brings developers together to share tools, research directions, and early dApp lessons. This helped coordinate a growing ecosystem and highlighted work on the project roadmap. Devcon also helped make Ethereum development feel like a shared public effort rather than a closed project.
Developers propose ERC-20, a standard interface for fungible tokens (tokens that are interchangeable, like dollars). A shared interface makes it easier for wallets, exchanges, and dApps to support many tokens without custom code for each one. This became a core building block for early token launches and later fundraising trends.
The Ethereum Foundation announces Homestead, described as the second major release, with a planned activation at mainnet block 1,150,000. Homestead bundles protocol and networking changes aimed at making Ethereum more stable and easier to upgrade. It also signaled increased confidence in the network’s security compared with Frontier.
The Homestead upgrade activates at block 1,150,000, moving Ethereum past the earliest “Frontier” stage. This upgrade introduced protocol changes (such as key EIPs for the release) that strengthened how the network operates. Homestead’s activation became an early example of Ethereum coordinating a planned network upgrade (“hard fork”) as the ecosystem grew.
ERC-137 publishes a specification for the Ethereum Name Service (ENS), aiming to map human-readable names to Ethereum resources like addresses and content hashes. This addressed a usability problem: raw addresses are long and error-prone for people to handle. ENS later became a widely used layer for more user-friendly Ethereum applications.
An attacker exploits a vulnerability in The DAO, a major Ethereum-based project, draining a large amount of ether from the contract. The event showed that smart contracts can fail because of coding mistakes, even if the underlying blockchain is working as designed. It triggered an urgent community debate over whether and how to intervene.
Ethereum performs an emergency hard fork at block 1,920,000 that moves DAO-related funds into a recovery contract so affected users can withdraw. Some participants reject changing chain history and continue the original chain, which becomes Ethereum Classic (ETC). This split made governance—who decides what the chain should do—a central topic for Ethereum’s early ecosystem.
After denial-of-service attacks and the ETH/ETC split, Ethereum schedules Spurious Dragon at block 2,675,000. One key change is EIP-155, which adds a “chain id” to transaction signatures to reduce replay attacks (where a transaction from one chain can be repeated on another). This helped stabilize early infrastructure like wallets and exchanges across multiple Ethereum-based networks.
The Byzantium hard fork activates at block 4,370,000, introducing multiple protocol improvements and changing the block reward from 5 to 3 ETH. The upgrade adds tools that make smart contracts safer and more expressive, and it delays the “difficulty bomb” (a mechanism intended to push future changes by making mining harder). By late 2017, this helped mark Ethereum’s transition from a fragile early network into a more mature platform supporting a growing token and dApp ecosystem.
Ethereum mainnet launch and early ecosystem (2015–2017)