Later this week, Ethereum will release its newest testnet, Holesky, in a bid to enhance the ecosystem’s testing capabilities. Along with the new network, Ethereum will wave goodbye to its largest existing testnet, Goerli.
Currently, Ethereum has two testnets: Goerli and Sepolia. The networks are like copies of the original Ethereum blockchain, but they are used specifically for testing new applications and simulating transactions.
Goerli and Sepolia are operated by a smaller subset of “validators” than the main Ethereum chain, and some developers think these smaller validator sets pose a problem: “We don't want to hit a scaling issue that could happen first on mainnet,” Parithosh Jayanthi, a devops engineer at the Ethereum Foundation, a non-profit focused on Ethereum research and development, told CoinDesk. “We want to catch [scaling issues] on testnet, which means we have to have a testnet that's bigger” than the main Ethereum chain.
Named for a train station in Prague, the goal of Holesky is to become bigger than mainnet Ethereum – meaning a larger set of validators should eventually operate the new network.
By making Holesky bigger, developers will theoretically be able to test infrastructure and upgrades under more rigorous conditions, meaning tests that go smoothly on Holesky should be less likely to face unforeseen issues on mainnet.
Sepolia, which is newer than Goerli and varies slightly in its design, is expected to remain the primary network for testing Ethereum-based applications. Holesky, on the other hand, is designed to take Goerli’s place as the main testing ground for Ethereum infrastructure and core protocol upgrades.
The new testnet comes after years of growth for Ethereum’s developer community. As more developers have flooded the ecosystem, Goerli hasn’t been able to meet the testing demands of increasingly complex infrastructure and upgrades.
The most visible issues with Goerli surround Goerli ETH (goETH), the test network’s native token. Whereas Ethereum’s mainnet charges ETH fees for every transaction, Ethereum’s testnets denominate fees in their own versions of ETH. The testnet ETH is like play money – used to run tests with lower financial stakes.
Goerli, unlike Sepolia, placed a hard cap on the total supply of its native goETH token. At times of high network demand, this cap can become an issue.
When the goETH cap was set in 2019, Goerli’s architects did not anticipate how much activity the network would eventually face – eventually becoming the primary testing ground for Ethereum’s massive Merge upgrade and subsequent developments to its proof-of-stake consensus system. “We didn’t pretty much know anything and it was impossible to predict exactly where Ethereum would be that far in the future,” Jayanthi told CoinDesk.
Goerli testers can request allotments of free goETH via online “faucets.” In February, however – as a result of the goETH supply cap – those faucets were unable to supply tokens quickly enough to meet demand. “We didn't know what type of supply issues were going to happen,” Jayanthi said.
Some Goerli testers were forced to turn to the open market to secure goETH, and at one point the fake ETH tokens cost as much as $1.60. The rising price of goETH became a significant bottleneck for developers since it greatly increased the cost of testing applications.
There were attempts to increase the supply of goETH, according to Jayanthi, but developers realized the root cause of the problem could only be addressed by starting an entirely new testnet with a better token issuance system.
“Let's start fresh. Now we have a lot more of an idea of what kind of network we want to build. And let's move forward with that,” Jayanthi said.
The goal with Holesky will be to support at least 1.4 million validators – more than currently operate Ethereum’s mainnet (700,000) and Goerli (512,000), combined. In addition to remedying some of the goETH supply problems, the larger validator set should allow developers and infrastructure providers to run tests under more realistic network conditions.
The testnet is already courting validators. Just as people “stake” ETH to become validators on Ethereum, they’ll be able to stake Holesky ETH to validate the new network.
The new network won’t be the last-ever revamp to Ethereum’s testing environment. “Holesky is going to launch now and then we're going to stop supporting it in 2028,” Jayanthi said. “We're kind of giving this information up front.”
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