TLDR: Fault proofs are now live on Base testnet, marking a step forward towards Stage 1 Decentralization.

Base launched with a vision to decentralize over time, and decentralization and scalability are some of our top priorities.

We’re now taking a step towards the next stage of decentralization: fault proofs are live on Base Sepolia testnet. Fault proofs enable anyone to make or challenge a proposal about the state of an L2 in a permissionless way. Today’s launch paves the way for bringing fault proofs securely to mainnet, and completing other milestones to reach Stage 1 Decentralization.

Fault proofs: A foundational step towards decentralization

Fault proofs improve decentralization in two major ways:

• Permissionless output proposals: In an L2 without fault proofs, only the centralized proposer (controlled by the chain operators) can create and submit claims about the state of the L2 to Ethereum. With fault proofs, anyone can make claims about an L2’s state instead of relying on a central party.

• Permissionless challenges to output proposals: If someone makes a faulty or fraudulent claim, anyone can challenge it.

Fault proofs are a foundational step towards more community-driven accountability and control, which reduces the need to place trust in a centralized party for state verification. As such, they are a key piece in a rollup’s progression towards decentralization.

Many rollups launch at Stage 0 (based on Vitalik’s definition) to balance security with decentralization, ensuring sufficient controls are in place as they grow and strengthen their infrastructure and ecosystems.

• Stage 0, or “full training wheels,” is a stage where all rollup transactions are posted on the L2, and the validity checks of these transactions are done by the chain’s operators. Therefore, state verification is centralized and dependent upon the chain operators.

• In Stage 1 decentralization, or “limited training wheels,” the chain state is verified with fault proofs but there is an override mechanism that can act in the event of a bug. The override mechanism requires consensus from both chain operators and a designated number of external stakeholders, which reduces the dependence on chain operators alone.

• In Stage 2 decentralization, changes to the L2 state only take place if a bug is uncovered, and any contract upgrades are subject to a 30 day delay (allowing those who disagree with an upgrade time to withdraw funds).

We’re super excited about the momentum in the L2 ecosystem towards decentralization (with most recently OP Mainnet reaching Stage 1). The evolution to Stage 1 highlights the importance of fault proofs in enhancing the transparency, security, and decentralization of Base by allowing broader participation in state verification and dispute resolution.

Getting to Stage 1 Decentralization

Launching fault proofs on Sepolia testnet provides an environment to run additional testing to help bring fault proofs to mainnet securely.

The other important step for Base to reach Stage 1 decentralization is to add the Security Council to our contract upgrade keys. This process further decentralizes the contract upgrade approval process we have today, extending it to a decentralized group of stakeholders beyond just Optimism and Base.

It also aligns us more closely with the Superchain vision: once this step is complete, Base can only make contract upgrades with actions taken by the Optimism Security Council, which only takes actions approved by Optimism Governance. We believe that the Optimism Security Council has the right controls and incentive structure in place to support the growth of the entire Superchain ecosystem and to continue building towards the vision of scaling Ethereum.

What’s next

Base’s commitment to decentralization and stability is a top priority, and this is a major next step in our decentralization journey. We’re excited to continue building on the Superchain vision of a more decentralized, better internet that’s accessible to everyone.