Ethereum’s Sepolia testnet completed its proof-of-stake Merge

Ethereum’s Sepolia public testnet completed its transition from proof-of-work to proof-of-stake on July 6, 2022, giving developers another full-network rehearsal for the planned Ethereum mainnet Merge. Sepolia was the second of three public testnets scheduled to make the transition after Ropsten; Goerli remained.

The milestone was consequential because the Merge was not a routine parameter change. It required Ethereum’s existing execution layer, which processed transactions and smart-contract state, to work with a separate proof-of-stake consensus layer responsible for choosing and finalizing blocks. Sepolia demonstrated that those layers and multiple client implementations could cross the transition together on a live public testing network.

It did not switch Ethereum mainnet to proof-of-stake, set a mainnet activation date or change any mainnet user balance on July 6.

How Sepolia crossed the Merge

The Ethereum Foundation’s published sequence had two stages. On June 20, 2022, the Bellatrix upgrade activated at epoch 100 on Sepolia’s Beacon Chain, preparing consensus clients to watch the proof-of-work execution chain. The second stage, Paris, was triggered when accumulated proof-of-work difficulty reached the selected Terminal Total Difficulty of 17,000,000,000,000,000.

At that threshold, proof-of-work block production stopped and the next execution payload was produced under Beacon Chain proof-of-stake consensus. The Foundation’s stated completion test was finalization of a post-threshold block, normally expected about two epochs, or roughly 13 minutes, after the first post-threshold block. Contemporaneous reporting placed the transition at about 14:00 UTC on July 6 and reported that the chain finalized.

The mechanism mattered operationally. Node operators needed both an execution client and a consensus client, connected through the Engine API and authenticated with a shared secret. A node updated on only one side could not participate correctly after the transition.

A successful test with a configuration warning

The result was best read as a successful rehearsal, not proof that every mainnet dependency was ready. Ethereum’s Protocol Support Team had revised its recommended go-ethereum and Erigon releases on July 5. Its notice said a regression made go-ethereum version 1.10.20 unsuitable for the Sepolia Merge and directed operators to a corrected build path.

After the transition, Ethereum protocol developer Terence Tsao reported that roughly 25% to 30% of validators went offline because of incorrect configurations, then returned as operators fixed them. That percentage was an attributable developer estimate reported on July 6, not an independently audited network measurement. The distinction matters: the transition and finalization succeeded, while the temporary participation loss exposed deployment risk around client settings.

Sepolia also had a permissioned validator set. It could test client interoperability, execution and finalization, but it did not reproduce the full range of independent validators, applications, infrastructure providers and economic incentives present on Ethereum mainnet. Goerli’s open validator set was intended to provide another test before any mainnet decision.

Why the milestone mattered

By July 6, the crypto market’s attention was dominated by falling asset prices and failures among centralized lenders. Sepolia supplied a separate kind of evidence: protocol engineering continued through the market contraction. The test reduced one category of uncertainty by showing that the designed transition could finalize on another public network, while identifying configuration work still needed before a larger deployment.

No Ether price or return is used here. Crypto trades continuously across venues, and the surviving protocol records do not establish that Sepolia caused a particular market move. The defensible event-day conclusion was technical: a second public testnet had merged, one public rehearsal remained, and mainnet timing was still unsettled.

Later confirmation

On July 27, 2022, the Ethereum Foundation described Sepolia as having transitioned to proof-of-stake and said only Goerli remained. That later statement confirms the July 6 milestone; it is not used to import a later mainnet schedule or outcome into the event-day record.