Ethereum developers have scheduled the Dencun network upgrade to activate on two additional test networks over the next two weeks, bringing the anticipated upgrade one step closer to mainnet.

Dencun – the largest Ethereum upgrade this year – will go live on two additional test networks, Sepolia and Holesky, on January 30 and February 7 respectively, according to a blog post published on Wednesday night by the Ethereum Foundation’s protocol support team.  

The announcement of Dencun’s expansion to two additional testnets came roughly a week after the network upgrade first went live on the Goerli testnet. The Dencun upgrade, named after Deneb, a star in the Cygnus constellation, and Cancun, the city location for Devcon 3, is expected to scale the Ethereum blockchain by implementing EIP-4844, also known as “proto-danksharding,” which introduces a new transaction type called a blob-carrying transaction. 

“A blob-carrying transaction is like a regular transaction, except it also carries an extra piece of data called a blob,” wrote Ethereum co-founder Vitalik Buterin on the community resource website “Blobs are extremely large (~125 kB), and can be much cheaper than similar amounts of calldata.” Ethereum developers expect the data space in these blobs to be used by rollups like Arbitrum and Optimism, which facilitate high-throughput transactions. 

As a result, Dencun is expected to lower the cost of transacting on Ethereum by allowing rollups, blockchain networks built atop Ethereum’s base layer, to add cheaper data to blocks. 

“Assuming the Sepolia and Holesky upgrades go well, Dencun will be scheduled on the Ethereum mainnet next,” the Ethereum Foundation said in its announcement.