1. Abstract Rollup is a scalability solution for Ethereum Layer 2, aiming to enhance the transaction throughput of Ethereum by processing transactions off-chain. Optimistic Rollup, as the name1. Abstract Rollup is a scalability solution for Ethereum Layer 2, aiming to enhance the transaction throughput of Ethereum by processing transactions off-chain. Optimistic Rollup, as the name
Optimistic Rollup: A Technical Analysis
1. Abstract
Rollup is a scalability solution for Ethereum Layer 2, aiming to enhance the transaction throughput of Ethereum by processing transactions off-chain. Optimistic Rollup, as the name suggests, employs an optimistic mechanism. Optimistic Rollup assumes that all transactions on Layer 2 are valid and compresses multiple transactions into a single submission to Ethereum. After the submission, there is a one-week period during which any user on the chain can challenge the authenticity of transactions. If fraud is detected during the state update, the challenger can receive a reward. Undoubtedly, Optimistic Rollup is the most practical and innovative solution for Ethereum Layer 2, and its technical details deserve further exploration. This article will provide a brief analysis of the implementation details of Optimistic Rollup and delve into its technical principles.
2. How Optimistic Rollup Works
On Optimistic Rollup Layer 2, user transactions are sent to the operators of Optimistic Rollup nodes. These nodes act as "validators" and "aggregators," responsible for aggregating and validating transactions. They compress multiple transactions' data into a single transaction, which, after compression, enters the transaction pool of Ethereum Layer 1, just like any other transaction. Finally, the nodes will receive and process the transactions and publish blocks on the Ethereum blockchain. Anyone can become an Optimistic Rollup node, but similar to the Proof-of-Stake (PoS) mechanism, nodes are required to provide a security deposit to the Ethereum network as a guarantee of their integrity.
During block submission, the nodes do not verify the legitimacy of state transitions. However, they provide a one-week "fraud proof" challenge period for the block. If no node or user challenges the legitimacy of the block during this period, the block will be confirmed. If a successful "fraud proof" challenge is made, the node that published the block will lose its security deposit. To incentivize the detection of fraudulent behavior, the security deposit is rewarded to the user who successfully proves the fraud. Through this approach, Optimistic Rollup utilizes the incentive measures of cryptographic economics to ensure the honesty and reliability of nodes.
3. How Data Compression is Achieved
A regular Ethereum transaction, such as sending ETH, typically consumes around 110 bytes. However, sending ETH on Optimistic Rollup only consumes approximately 12 bytes. To achieve this, Optimistic Rollup employs simpler advanced encoding techniques.
In Optimistic Rollup Layer 2 transactions, the nonce is completely omitted and instead recovered from the pre-state. Gas-related information like Gasprice and Gas is moved out of Layer 2 transactions. The To and From fields no longer require Ethereum addresses; instead, a subtree is added to the state to store the mapping of indices to addresses. Value can be stored using scientific notation, requiring only 3 digits for transfers. As for signatures, transactions within a batch can be aggregated using BLS aggregate signatures, reducing the storage consumption for each individual transaction signature. This aggregated signature can batch-check the entire set of messages and senders. Additionally, these transaction data are stored in the Calldata field on-chain, which has a relatively low gas cost.
The uploaded data includes not only the aforementioned transaction data and content, but also the Merkle tree root before and after batch transactions (including state data such as account, balance, and contract code, thus known as the state root). It also includes data used to prove (or verify) the legitimacy of state transitions. These compression techniques are crucial for achieving scalability using Optimistic Rollup. Currently, after compression, Optimistic Rollup can provide throughput that is over 30 times higher than Ethereum.
4. Submitting Data to Ethereum
Optimistic Rollup deploys a specific smart contract called the Rollup contract on Ethereum Layer 1. This contract is responsible for managing the state of the Rollup, including tracking user balances, handling deposits, withdrawals, and dispute resolution. In Optimistic Rollup, transactions are collected and aggregated by nodes off-chain, bundling multiple transactions into a "Rollup block." This block contains transaction content and the Merkle tree root of the new account state.
Later on, nodes publish the aggregated data as calldata on Ethereum. Calldata is an unmodifiable and non-persistent area within smart contracts, similar to internal storage. As part of the history log of blockchain, calldata is not stored as part of Ethereum's state. As calldata doesn't involve any portion of Ethereum's state, it is more cost-effective to store data on-chain using calldata.
5. State Commitment
As mentioned before, the uploaded data includes not only the transaction content but also the Merkle tree root before and after the transaction. The Merkle tree root represents the Optimistic Rollup state at any given point in time, including accounts, balances, contract codes, etc. It is also known as the "state tree" and serves as the organizational form of the Optimistic Rollup state. The leaf nodes of the Merkle tree represent the account states, and the root node represents the final value. Changes in the Layer 2 transactions of Optimistic Rollup result in updates to the account states, which in turn affect the information of the leaf nodes, ultimately leading to changes in the root hash value. The Layer 2 operator maintains the state tree of Layer 2 accounts locally, recording the root hash values before and after the batch transactions occur, and uploads this root hash value when uploading the batch transactions.
This Merkle tree root (state root) references the latest state of the Rollup, undergoes hashing, and is stored in the Rollup contract. Each on-chain state transition generates a new Rollup state, and nodes submit this state by computing the new state root.
When nodes publish a block, they need to submit both the old state root and the new state root. If the old state root matches the existing state root in the on-chain contract, the latter is discarded and replaced with the new state root. Nodes also need to submit the Merkle tree root for the batch of transactions itself. This allows anyone to prove that the transactions are included in the block by providing a Merkle tree proof. The Merkle tree root is crucial for proving the state changes in Optimistic Rollup.
6. Fraud Proof
Optimistic Rollup allows anyone to provide transaction information and state transition information, and publish blocks without providing validity proofs. To ensure the security of the Ethereum blockchain, Optimistic Rollup has established a one-week window during which users can raise doubts about the blocks (including state transitions and other information).
If someone raises a doubt, the Optimistic Rollup protocol initiates fraud proof computation. By replaying the transactions that resulted in state transitions on the chain, a new state root is computed. This computed state root is then compared with the state root proposed by the sequencer. If other nodes or users discover a discrepancy between the final block state and the state proposed by the node, the fraud proof challenge is successful, and the state transition is canceled. At the same time, the challenging node is penalized, and their bond is confiscated and awarded to the challenger.
Re-executing transactions on Ethereum to detect fraud requires publishing state commitments for individual transactions and adding data that must be published on-chain. Replaying transactions also incurs significant gas costs. Currently, the challenge period for Optimistic Rollup is one week, but due to capital efficiency concerns, the community is actively discussing whether to shorten the challenge period.
7. OVM Virtual Machine
Optimistic Rollup not only supports the scalability of Ethereum but also incorporates the entire functionality of Ethereum smart contracts into the Layer2 framework, providing a Turing-complete OVM virtual machine for the development and deployment of dApps.
The OVM virtual machine is a feature-complete execution environment that is fully compatible with the Ethereum EVM virtual machine and designed for Layer2 systems. With the OVM virtual machine, developers can perform all Ethereum on-chain operations on the Rollup chain and interact with the blockchain through APIs. Additionally, the OVM virtual machine simplifies the process of porting dApps to Layer2. Instead of deploying various Layer2 scaling solutions, project teams can simply integrate with OVM and utilize its various Layer2 structures.
8. Conclusion
There are two Layer2 networks developed based on the Optimistic Rollup protocol: Optimism and Arbitrum. Currently, Optimism and Arbitrum are the largest Layer 2 ecosystems in the Ethereum space, with a total locked value of $4 billion and still experiencing significant growth. Many well-known projects have also joined the Optimistic Rollup camp, such as UniSwap, SushiSwap, and others.
However, Optimistic Rollup is not the only player on the field and faces competition from ZK Rollup. As mentioned earlier, Optimistic Rollup relies on fraud proofs, where the system optimistically believes in the correctness of transaction data and ensures transaction validity through the economic logic of fraud challenges. On the other hand, ZK Rollup is a scalability solution based on zero-knowledge proofs, where off-chain transactions are processed in batches and cryptographic validity proofs are generated to verify the authenticity of each batch of transactions. The superiority of one over the other requires further examination over a longer period of time.
Market Opportunity
4 Price(4)
$0.00903
$0.00903$0.00903
USD
4 (4) Live Price Chart
Popular Articles
View More
USDJPY Forecast After the July 30, 2026 Yen Surge: Why the Dollar Fell and What Comes Next
USDJPY experienced an unusually sharp reversal during the evening of July 30, 2026, Hong Kong time. The U.S. dollar fell by as much as 3% against the Japanese yen, briefly pushing USDJPY down to
Highest Leverage Crypto Exchanges in 2026: Only Two Survive the 500x Test
Two major crypto exchanges currently sit at the top of the leverage ladder: MEXC and BTCC both list futures contracts at up to 500x, while most large rivals cap out between 100x and 125x. MEXC pairs
Can You Trade Stocks and Crypto in One App? Best Platforms Compared (2026)
Yes, you can trade stocks and crypto in one app, but your real options depend on where you live. US residents can pick from Robinhood, Coinbase, Kraken, or Crypto.com. UK and EU investors have eToro
Hot Crypto Updates
View More
Microsoft FY2026 Q4 Earnings Beat Estimates as Azure Growth Accelerates and MSFT Stock Jumps
When Were the Microsoft Q4 FY2026 Earnings Released? Microsoft announced its fiscal fourth-quarter 2026 earnings after the U.S. market closed on Wednesday, July 29, 2026. The quarter covered the
SPY Price Prediction 2026–2030: Bull, Base and Bear Market Scenarios
Summary SPY closed at $740.86 on July 28, 2026. State Street reported a forward P/E of 21.59x and estimated three-to-five-year portfolio earnings growth of 17.38%. The following ranges are
STM Stock Price Prediction 2026–2030: Bull, Base and Bear Scenarios
Summary STM closed near $53.45 on July 27, 2026 after falling sharply following Q2 earnings. The stock had previously reached approximately $81.42 in early June, illustrating the unusually wide range
Trending News
View More
Samsung Q2 Profit Jumps 19x, But Shares Fall: Why AI Memory Stocks Face a Higher Bar
Samsung Electronics recently guided its Q2 2026 revenue at approximately KRW 171 trillion with an operating profit of KRW 89.4 trillion—an astonishing 19-fold jump from a year earlier. On paper, this
Tesla Q1 2026 Earnings Review: Deliveries Rebounded, But Margin Quality Remains the Real Test
Tesla reported its Q1 2026 financial results on April 22, 2026, after the U.S. market close. The company delivered 358,023 vehicles in the quarter, generated total revenue of $22.4 billion, and report
Apple FY2026 Q2 Earnings Review: iPhone Revenue and Services Growth Keep EPS Story Intact
Apple reported fiscal 2026 second-quarter results on April 30, 2026, covering the quarter that ended March 28, 2026. Revenue reached $111.2 billion, up 17% year over year, while diluted EPS rose 22% t
Hyperliquid Open Interest Hits $11.5 Billion: Are On-Chain Perpetuals Expanding into U.S. Equity Markets?
Hyperliquid’s open interest has reached approximately $11.5 billion, a new high for 2026, with HIP-3 markets contributing nearly $4 billion. The S&P 500-linked contract has become the largest HIP-3 ma
Related Articles
View More
MEXC Alpha Trader Research Weekly | Bulls vs. Bears Clash Ahead of FOMC: Is BTC's $63K Critical Support a Golden Buying Opportunity or a Bottomless Pit?
Week 4, July 2026Reporting Period: Jul 22, 2026 – Jul 28, 2026Data cutoff: Jul 28, 2026Core NarrativeLast week, the crypto market experienced a dramatic shift from optimism to caution. Early in the we
Unlocking the Long Tail: MEXC's Full-Spectrum Trading Universe
In the cryptocurrency market, trading in major players like BTC and ETH have become fiercely competitive, while the real opportunities for outsized returns often lie in underexplored long-tail assets.
MEXC Alpha Trader Research Weekly | ETFs See Net Inflows for Two Consecutive Weeks as BTC Reclaims $65K: Bottoming Signal or False Breakout?
Week 3, July 2026Reporting Period: July 15 – July 21, 2026Data Cutoff: July 21, 2026Market OverviewThe crypto market demonstrated resilience this week amidst complex multi-directional pressures. Bitco
U.S. Stocks Weekly Report | Jul 11–Jul 17: CPI Plunges 3.5%, Top Three Banks Post Strongest Q2 Ever: Inflation Turning Point Combined with AI Profit Surge Opens Valuation Reset Window for Growth Stocks
On July 17, 2026, a rare macroeconomic combination unfolded intensively within the same week: The US June Consumer price index（CPI） annual rate stood at 3.5%, significantly lower than the expected 3.8
