Base cuts block times to 0.2 seconds on testnet with Flashblocks, mainnet rollout expected in Q2

Coinbase's Layer 2 chain Base has implemented a technology called Flashblocks on testnet, which reduces effective block times on the network from 2 seconds to 200 milliseconds.

Flashblocks are currently available for testing on the Base Sepolia testnet and are expected to move to the mainnet in the year's second quarter. They use preconfirmation blocks streamed every 200 milliseconds for quicker transaction processing with early confirmations and revert protection.

This tenfold improvement in speed aims to boost scalability and usability for developers and users within the Base ecosystem. 

Flashblocks was developed in collaboration with Flashbots, a research and development group known for its work on Ethereum’s transaction ordering and MEV solutions. Uniswap also leveraged the same technology to implement 0.25-second block times on Layer 2 Unichain .

Flashblocks are part of a trio of new tools announced by Base at ETHDenver 2025, alongside Base Appchains and Smart Wallet Sub Accounts that are currently in development.

Appchains are customizable, application-specific blockchains built on top of the Base Layer 2 network built on the OP Stack, the team explained. 

These will work as Layer 3 chains — or rollups within a rollup — that provide dedicated block space to help apps scale. They will be customizable, with options for custom gas tokens and fee logic, and are targeted at high-traffic apps.

The team also introduced Smart Wallet Sub Accounts, which allow users to manage multiple on-chain wallets from a single interface.

Base is an optimistic rollup that processes transactions off the main Ethereum blockchain and only periodically posts transaction data on-chain. It's the most widely used Layer 2 chain on Ethereum by daily active users.