Ethereum Schedules Final Testnet Merge Ahead of Mainnet Proof-of-Stake Switch
The Ethereum Foundation announced on July 27, 2022, that the Goerli test network would merge with the Prater beacon chain. The merge completed approximately two weeks later, on August 11, 2022, at approximately 01:45 UTC, completing the third and final rehearsal before Ethereum's full transition away from energy-intensive proof-of-work mining. That completion cleared the path to a mainnet transition that would ultimately cut Ethereum's energy consumption by an estimated 99.95%.
The merge proceeded in two distinct on-chain steps. The first, called Bellatrix, upgraded the Prater consensus layer (the part of the network that coordinates validator agreement) at epoch 112,260, triggering around 12:24 PM UTC on August 4, 2022. The second step, called Paris, activated on the execution layer once the network's total accumulated proof-of-work score, counted since genesis, crossed a preset threshold of 10,790,000, referred to as the Terminal Total Difficulty, or TTD. From the moment the first block was produced by a proof-of-stake validator, finalization took roughly 13 minutes. After completion, the Prater name was retired and the merged network carried forward as Goerli alone.
The Ethereum Foundation set an unusually wide trigger window for Paris, estimating the TTD would be reached somewhere between August 6 and August 12. Tim Beiko, Protocol Support Lead at the Ethereum Foundation, explained the uncertainty in a statement to CoinDesk: "It's hard to predict the behavior of the merge." Goerli had used proof-of-authority consensus to produce blocks before the transition, adding to the difficulty of forecasting the exact trigger moment. The final event landed on August 11, within that window.
Goerli's significance in the merge sequence went beyond its place in the schedule. Unlike Ropsten, which merged in June 2022, or Sepolia, which followed in July, Goerli was the largest community testnet. It hosted real developer tooling, active decentralized applications (dApps), and a substantial validator set, making it the closest available simulation of mainnet conditions. Developers and node operators running infrastructure on Goerli needed to upgrade their client software before the Bellatrix epoch. Required versions spanned both consensus and execution layers: on the consensus side, these included Prysm v2.1.4-rc.0, Lighthouse v2.4.0, Lodestar v0.41.0, Nimbus v22.7.0, and Teku 22.7.0; on the execution side, Geth v1.10.21, Besu 22.7.0-RC3, Erigon 2022.07.04-alpha, and Nethermind 1.13.5. Operators also had to configure a fee recipient address to receive transaction priority fees after the merge. As the Ethereum Foundation noted in its announcement: "Set the fee recipient as part of your validator client configurations."
The merge also introduced two technical changes relevant to developers building on the network. The DIFFICULTY opcode (code reference 0x44) returned the block difficulty value; some smart contracts consumed it as a source of on-chain randomness. Post-merge, the opcode was renamed PREVRANDAO, delivering a proper beacon-chain RANDAO-derived value in place of the mining difficulty figure. Any application relying on the old opcode required a code audit before the mainnet transition, as applications expecting a large difficulty number would receive a 256-bit RANDAO value instead. A new JSON-RPC block tag, "finalized", was also introduced, allowing developers to query the most recently finalized block rather than just the latest one.
Africa and South Asia each brought substantial independent momentum to the Goerli merge. Blockchain funding across Africa surged more than 1,600% in 2022 year-over-year, topping $1 billion, with the vast majority of activity on Ethereum-compatible chains. Goerli served as the primary staging environment for that work. The period also saw organized Ethereum developer infrastructure take root across the continent: Ethereum Nigeria joined the ETHGlobal network, establishing a named institutional anchor for the region's growing builder community. The opcode change and new RPC tag meant developers building EVM-compatible (Ethereum Virtual Machine) applications needed to audit their code before the mainnet transition. In India, which accounted for approximately 12% of global blockchain developers by 2023, the Goerli merge was directly relevant to DeFi and infrastructure teams relying on testnet tooling. ETHIndia, the world's largest Ethereum hackathon, had produced hundreds of real-world Web3 protocols and tools running on Goerli testnet infrastructure, grounding the merge's technical stakes in a specific and substantial developer base. The merge also raised the technical requirements for node operators: running a post-merge Ethereum node required pairing an execution client with a consensus client and linking them through the Engine API using JWT authentication, an added layer that increased setup complexity and hardware demands for builders running infrastructure on lower-cost equipment.
The Ethereum Foundation's documentation and the Prater Staking Launchpad's Merge Readiness Checklist were the primary self-assessment tools available to operators at the time, though both were published in English only at launch.
With Goerli complete and only Sepolia and Goerli retained as active testnets going forward, the Ethereum Foundation moved quickly. The mainnet Merge was announced on August 24, 2022, with Bellatrix set for epoch 144,896 on September 6 and a TTD of 58,750,000,000,000,000,000,000 for the Paris execution layer transition. The mainnet Merge completed on September 15, 2022, dropping Ethereum's per-transaction carbon footprint from roughly 109.71 kg of CO₂ to approximately 0.01 kg of CO₂, and reducing the network's total annual energy use to around 0.0026 TWh per year.
Sources: Ethereum Foundation Blog (July 27 and August 24, 2022); CoinDesk (August 3 and August 11, 2022); Ethereum.org; Consensys; Ecofin Agency; Outlook India; TechBuild Africa; Web3Africa.tech.