Ethereum activated its highly anticipated “Fusaka” upgrade on Wednesday, marking the blockchain’s second major code change of 2025.

The update is designed to help Ethereum handle the increasingly large transaction batches coming from the layer-2 networks that settle on top of it.

The Fusaka upgrade, also sometimes called a “hard fork”, was triggered at 21:49 UTC and finalized roughly after 15 minutes, indicating that the code changes landed smoothly. Many of the core developers were gathered to celebrate the occasion on the EthStaker livestream.

Fusaka – a blend of the names Fulu + Osaka – bundles two hard forks on Ethereum happening in tandem: one on the consensus layer and one on the execution layer. The former is where transactions and smart contracts run, while the settlement layer is where these transactions are verified, finalized, and secured.

At the center of the upgrade is PeerDAS, a system that lets validators check small slices of data rather than entire “blobs,” reducing both costs and computational load for validators and layer-2 networks.

Today, layer 2s submit their transaction data to Ethereum in the form of blobs, which validators must download and verify in full. That process contributes to congestion and slows down the network. PeerDAS changes this by allowing validators to verify only a small portion of the blob’s data, which speeds up the verification process and thus reduces the gas fees tied to the processing.

Beyond layer 2s, the upgrade is expected to lower the barrier for smaller or newer validator operators by cutting down the resources required to run just a few validators. Still, Ethereum developers note that institutions operating large fleets of nodes, such as staking pools, won’t see the same level of savings.

“The improvements will take a few months to fully play out, since we will only slowly increase the blobs in order to make sure the network can handle the increased throughput safely,” Marius Van Der Wijden, a core developer at the Ethereum Foundation, told CoinDesk over Telegram.

Ethereum developers moved quickly to ship the upgrade this year as the ecosystem grapples with a reputation for slow or delayed rollouts. The goal was to land a series of smaller improvements now while preparing for more ambitious changes ahead.

“PeerDAS’ importance was such that, during the initial development of the Fusaka upgrade, any feature that carried a risk of delaying the fork, such as those requiring more research or having high complexity, was deprioritized and removed from the scope,” said Gabriel Trintinalia, an Ethereum core developer and engineer at Consensys. The “Fusaka upgrade really shows that Ethereum is serious about making Mainnet faster.”

Traditional financial (TradFi) institutions are taking notice as well. Last month, Fidelity Digital Assets published a report describing Fusaka as a decisive step toward a more strategically aligned and economically coherent roadmap for Ethereum.

What else is in Fusaka?

While the main focus of Fusaka is PeerDAS, there are 12 other Ethereum Improvement Proposals (EIPs) that have made it into the package, mostly improving the experience for developers and the health of the network. These include:

• EIP-7642: Removes old, no longer used fields from Ethereum’s networking messages to simplify and clean up the protocol.
• EIP-7823: Puts a maximum limit on how big certain math operations can be so they can’t overload the network.
• EIP-7825: Sets an upper cap on how big a single transaction can be so no one can include extremely large, resource-heavy transactions.
• EIP-7883: Makes a specific type of math operation more expensive in gas so heavy calculations don’t unfairly strain the network.
• EIP-7892: Allows future upgrades to change only blob-related settings without touching the rest of the protocol, making blob tuning safer and easier.
• EIP-7910: Adds a new API method that lets software easily check what configuration or rules a node is using.
• EIP-7917: Makes the process of predicting who will propose the next blocks more transparent and reliable.
• EIP-7918: Makes sure blob data fees stay aligned with the actual cost of processing them, preventing extreme price swings.
• EIP-7934: Adds a strict size limit to certain block data to stop overly large blocks from slowing down the chain.
• EIP-7935: Raises the default block gas limit to 60 million so the network can fit more computation in each block.
• EIP-7939: Adds a simple new instruction for smart contracts that lets them improve efficiency for some calculations.
• EIP-7951: Adds built-in support for a widely used cryptographic signature type.

As for what’s next, developers are already scoping out on the network’s next big upgrade, Glamsterdam, but nothing has been finalized yet for when it will occur and what will go in it.

Read more: Ethereum’s Fusaka Upgrade Could Cut Node Costs, Ease Adoption