Optimistic Rollups (e.g., Arbitrum, Optimism) excel at providing low, predictable base fees by leveraging Ethereum's data availability. Their security model—posting fraud proofs only in case of a dispute—keeps transaction costs consistently low for users. For example, Arbitrum One's average transaction fee often sits below $0.10, making it a staple for high-frequency DeFi protocols like GMX and Uniswap. This stability stems from batching thousands of transactions into a single, inexpensive L1 calldata post.
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Comparisons
Optimistic vs ZK Rollups: Fee Stability
A technical analysis comparing the transaction cost predictability of Optimistic and ZK Rollups, focusing on L1 dependency, fee volatility, and long-term scaling economics for CTOs and architects.
Chainscore © 2026
introduction
THE ANALYSIS
Introduction: The Fee Stability Imperative
Understanding the divergent fee models of Optimistic and ZK Rollups is critical for building predictable, cost-effective applications.
ZK Rollups (e.g., zkSync Era, StarkNet) take a different approach by using validity proofs, which require significant computational overhead to generate. This results in a prover fee added to the base data cost, creating more variable and historically higher user fees. However, this trade-off delivers superior finality—transactions are settled on Ethereum in minutes, not days. Protocols like dYdX and Immutable X prioritize this security and speed for financial and gaming applications, accepting the fee volatility.
The key trade-off: If your priority is minimizing and stabilizing end-user transaction costs for social or high-volume DeFi apps, choose an Optimistic Rollup. If you prioritize instant finality and maximal security, and your application's economics can absorb higher, more variable proving costs (e.g., high-value NFT minting, institutional finance), a ZK Rollup is the stronger choice. The landscape is evolving, with ZK Rollups like zkSync implementing fee abstractions to improve stability.
tldr-summary
Optimistic vs ZK Rollups
TL;DR: Key Differentiators at a Glance
A direct comparison of fee stability mechanisms, trade-offs, and ideal use cases.
01
Optimistic Rollups: Lower Fixed Costs
Predictable L1 Data Fees: Fees are dominated by the cost of publishing transaction data (calldata) to Ethereum L1, which is stable and predictable. This makes gas estimation simpler for end-users.
- Example: Arbitrum One and Optimism base fees are primarily L1 calldata costs plus a small L2 execution fee.
- Best for: Applications where cost predictability is more critical than absolute minimum cost, such as high-frequency DeFi protocols or payroll systems.
02
Optimistic Rollups: Withdrawal Delay Risk
7-Day Challenge Period Creates Volatility: While L2 fees are stable, moving assets back to L1 requires waiting for the fraud-proof window. Users relying on third-party liquidity bridges (like Hop, Across) pay a variable premium during high demand, introducing fee instability for withdrawals.
- Trade-off: Stable operating costs vs. unpredictable exit costs.
- Matters for: Protocols with frequent cross-chain liquidity movements or users who prioritize instant L1 liquidity.
03
ZK Rollups: Highly Variable Proving Costs
Proof Generation Cost is Volatile: A significant portion of the transaction fee pays for zero-knowledge proof generation (SNARK/STARK). This cost fluctuates with off-chain compute market prices and proof complexity, adding a variable layer to fees.
- Example: zkSync Era and StarkNet fees can spike during network congestion due to prover competition.
- Best for: Applications where trustless, fast withdrawals (30 min to 1 hr) are worth the variable cost premium, such as centralized exchange off-ramping or gaming asset bridges.
04
ZK Rollups: Long-Term Fee Stability Potential
Path to Cheaper, Stable Fees with EIP-4844: ZKRs stand to benefit more from Ethereum's data sharding (blobs). Smaller proof sizes combined with large, cheap data blobs could decouple fees from L1 calldata volatility.
- Future Outlook: With recursive proofs and specialized hardware, proof generation costs may stabilize.
- Matters for: Architects planning 2+ year horizons who are betting on Ethereum's roadmap to reduce ZKR's primary cost variable.
OPTIMISTIC VS ZK ROLLUPS
Fee Stability Feature Matrix
Direct comparison of key fee-related metrics and mechanisms for L2 scaling solutions.
| Metric | Optimistic Rollups (e.g., Arbitrum, Optimism) | ZK Rollups (e.g., zkSync Era, StarkNet) |
|---|---|---|
Fee Predictability | ||
Avg. L1 Data Cost per Tx | $0.10 - $0.40 | $0.20 - $0.60 |
Withdrawal Time to L1 | ~7 days | < 1 hour |
Native Fee Token | ETH | Varies (ETH, USDC, etc.) |
Proof Generation Cost | N/A | $0.05 - $0.15 per batch |
Gas Fee Spikes During Congestion | High | Moderate |
pros-cons-a
FEE DYNAMICS COMPARISON
Optimistic vs ZK Rollups: Fee Stability
A technical breakdown of how Optimistic (Arbitrum, Optimism) and ZK (zkSync, StarkNet) rollups handle transaction costs, highlighting key trade-offs for protocol architects.
01
Optimistic Rollups: Predictable Base Fees
Lower, stable L1 data costs: Fees are primarily the cost to post calldata to Ethereum (e.g., Arbitrum One). This cost is predictable and scales linearly with transaction size, avoiding the computational overhead of proof generation. This matters for general-purpose dApps where user experience depends on consistent, understandable fee quotes.
~$0.10 - $0.50
Typical Swap Fee
1-7 Days
Withdrawal Delay
03
ZK Rollups: Eliminated Withdrawal Tax
No challenge period, no bridge premium: Validity proofs provide instant finality to L1, enabling trustless withdrawals in minutes (e.g., zkSync Era ~ 1 hour). This removes the liquidity provider fee entirely, a decisive advantage for high-frequency traders, arbitrage bots, and protocols managing treasury flows.
< 1 Hour
Trustless Withdrawal
0%
LP Bridge Fee
pros-cons-b
Optimistic vs ZK Rollups
ZK Rollups: Fee Stability Pros & Cons
A data-driven comparison of transaction cost predictability between the two dominant scaling architectures.
01
Optimistic Rollups: Lower Baseline Fees
Specific advantage: Lower computational overhead for state validation. Without expensive ZK-proof generation, networks like Arbitrum One and OP Mainnet maintain average transaction fees under $0.10 during normal load. This matters for high-volume, low-value applications like social interactions or micro-transactions where absolute cost is the primary constraint.
< $0.10
Avg. L2 Fee
02
Optimistic Rollups: Unpredictable Surge Pricing
Specific disadvantage: Direct exposure to L1 gas volatility. During Ethereum mainnet congestion, the cost to post fraud-proof data or state batches spikes. This creates unpredictable, correlated fee surges for users, as seen in events like major NFT mints. This matters for businesses requiring stable operating costs or protocols with predictable fee models.
03
ZK Rollups: Predictable Finality Cost
Specific advantage: Fee calculation is independent of L1 settlement timing. Once a ZK-proof (e.g., a STARK or SNARK) is generated and verified on L1, the cost is known and fixed. Networks like zkSync Era and Starknet decouple user transaction fees from the volatile cost of proof submission. This matters for financial applications like DEXs and lending that need reliable margin calculations.
04
ZK Rollups: Higher Fixed Proof Cost
Specific disadvantage: Significant computational overhead for proof generation. This creates a higher fixed cost floor that must be amortized across a block. For low-activity periods, this can make simple transactions more expensive than on Optimistic Rollups. This matters for new or niche chains with lower transaction volume where proof cost distribution is less efficient.
~500K gas
Proof Verification Cost
CHOOSE YOUR PRIORITY
When to Choose: Decision Framework by Use Case
Optimistic Rollups for DeFi
Verdict: The current standard for high-value, complex applications. Strengths:
- Battle-Tested: Protocols like Arbitrum and Optimism host billions in TVL, with proven security models for AMMs (Uniswap, Curve) and lending markets (Aave, Compound).
- EVM-Equivalence: Seamless deployment with minimal code changes, leveraging existing Solidity tooling (Hardhat, Foundry).
- Cost Predictability: Fees are stable and low relative to L1, with clear cost structures for complex contract interactions. Trade-off: 7-day withdrawal delay requires liquidity bridge solutions (e.g., Hop Protocol, Across).
ZK Rollups for DeFi
Verdict: Emerging leader for high-frequency, low-latency trading. Strengths:
- Instant Finality: Sub-minute withdrawals to L1 are game-changing for arbitrage and capital efficiency on zkSync Era and StarkNet.
- Native Account Abstraction: Better UX for batch transactions and sponsored gas, as seen in dYdX (on StarkEx).
- Superior Scalability: Higher theoretical TPS prepares for future DeFi mass adoption. Trade-off: Less mature tooling and higher proving costs for general-purpose, complex smart contracts.
OPTIMISTIC VS ZK-ROLLUPS
Technical Deep Dive: How Architecture Drives Fee Volatility
The core architectural differences between Optimistic and ZK-Rollups create distinct fee profiles and volatility patterns. This analysis breaks down how fraud proofs, data availability, and proof generation directly impact cost stability for end-users and developers.
For simple transfers, ZK-Rollups are typically cheaper. They submit validity proofs, eliminating the need for a lengthy, capital-intensive challenge period. However, for complex smart contract interactions, Optimistic Rollups like Arbitrum or Optimism can be cheaper because they avoid the high computational cost of generating ZK-SNARK/STARK proofs for complex logic. Fees are ultimately dictated by the cost of publishing data to Ethereum L1.
verdict
THE ANALYSIS
Verdict: Strategic Recommendations
Choosing between Optimistic and ZK Rollups for fee stability is a strategic decision that hinges on your application's tolerance for latency, cost structure, and user experience.
Optimistic Rollups (like Arbitrum and Optimism) excel at providing predictable, low-cost transactions for general-purpose smart contracts because they rely on computationally cheaper fraud proofs. For example, Arbitrum One's average transaction fee is typically under $0.10, offering a stable and affordable environment for high-volume DeFi protocols like GMX and Uniswap. Their primary cost is the mandatory 7-day challenge period for withdrawals, which introduces latency but keeps on-chain verification costs minimal.
ZK Rollups (like zkSync Era and StarkNet) take a different approach by using validity proofs, which are computationally intensive to generate but cheap to verify. This results in a trade-off: higher prover costs for sequencers can lead to more variable fees during network congestion, but finality is near-instant (minutes vs. days). Their architecture is exceptionally efficient for simple payments and swaps, as seen with dYdX's migration to a ZK Rollup, which targets sub-$0.01 fees for its core orderbook operations.
The key trade-off: If your priority is maximizing developer flexibility and achieving the most stable, low-cost environment for complex, general-purpose dApps, choose an Optimistic Rollup. If you prioritize instant finality, superior scalability for specific transaction types, and are willing to manage a more complex cost model for a better end-user experience, a ZK Rollup is the forward-looking choice. For CTOs, the decision map is clear: Optimistic for today's battle-tested cost predictability; ZK for tomorrow's architectural edge in user experience.
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