Optimism’s “Fault Proof” System Officially Launches on Mainnet

What is Optimism?

Optimism is a leading Layer 2 blockchain designed to help Ethereum users transact quickly and at lower costs. Its technology underpins major blockchain projects, including Coinbase’s popular Base blockchain and Worldcoin’s World Chain, created by OpenAI founder Sam Altman.

For years, Optimism has faced a critical issue: while its blockchain networks rely on Ethereum’s security, a core feature—”fault proofs”—was missing. This long-promised technology has now finally been deployed on Optimism’s mainnet as of Monday.

Why Introduce Fault Proofs?

Fault proofs ensure the integrity of Layer-2 chains based on Optimism. They prevent operators from submitting inaccurate transaction data to Ethereum’s Layer-1 ledger and support the “decentralized” withdrawal mechanism of Layer-2 chains.

All Layer 2 Rollup networks, including Optimism’s rival Arbitrum, use similar proof technologies to ensure the accuracy of user transactions and withdrawals. Fault proofs give users the confidence to trust Ethereum’s extensive operator network over the Rollup’s internal systems for transaction and withdrawal accuracy.

With Arbitrum and other Layer 2 chains already having their proof systems, Optimism lagged behind, making it subject to criticism. Now, with fault proofs live on the mainnet, Optimism aims to move past these criticisms.

How Fault Proofs Work

In the past two years, Layer 2 Rollup networks like Optimism have become a popular method for transactions on the expensive Ethereum blockchain. When users submit transactions to a Rollup network, these transactions are bundled together and then sent to Ethereum. This bundling allows faster transactions at a fraction of the cost.

Theoretically, Rollup transactions are protected by “proofs,” a cryptographic method that lets observers on Ethereum verify the accuracy of transaction details, crucial for withdrawals. Without fault proofs, users had to trust the Rollup’s “security council” to return their funds, exposing the Rollup to potential human error or bias. Fault proofs allow users to trust only Ethereum.

Optimism’s name comes from its “Optimism” proof system, first introduced in 2021, but quickly discarded after issues were found. OP Labs CEO Karl Floersch explained that the entire system was redesigned and rewritten from scratch. After thorough testing and audits, including by blockchain security firm Sherlock, the system is now considered ready for prime time.

The Fault Proof Progress

Starting this week, the network will use the fault-proof system to power withdrawals but will retain “training wheels” to ensure smooth operation. The security council will remain to intervene if the fault-proof system fails. This combination is termed “Phase 1 decentralization” by Optimism.

The ultimate goal is “Phase 2 decentralization,” where the network operates without reliance on the security council. This stage involves multiple fault-proof systems working together, akin to an autopilot system. While the team is working towards this goal, no timeline has been provided.

With fault proofs now on Optimism’s mainnet, other blockchains using Optimism’s OP Stack will also gain access to this technology. According to DefiLlama, current blockchains using the OP Stack, like Blast and Base, already surpass Optimism’s mainnet in total value locked.

“We’re starting this upgrade with the OP mainnet, which is quite significant,” Floersch noted, adding that Coinbase’s Base chain will implement the fault-proof system shortly.