Top Ethereum L2s Compared (2025): Performance, Fees, Security, and Builder UX

1) Why L2s exist, and what changed after EIP-4844

Ethereum’s base layer (L1) optimizes for security and decentralization. That limits throughput and keeps fees relatively high when demand spikes. Layer 2 rollups move execution off-chain (or off-L1), then bring back the result to L1 under a proof system. Two major approaches dominate:

• Optimistic rollups assume batches are valid by default and give a challenge window to dispute fraud. Examples: Arbitrum, OP Mainnet/Optimism, and Base.
• ZK rollups submit validity proofs that mathematically attest to correctness of state updates. Examples: zkSync Era, Starknet, Scroll, Linea.

In March 2024, Ethereum shipped EIP-4844 (proto-danksharding), introducing blob space, a cheaper data lane purpose-built for rollups. Rollups post compressed transaction data into blobs; users then benefit from lower fees. But keep in mind: your actual fee depends on how much data your transaction generates and the rollup’s compression strategy. Not all L2s compress equally, and blob prices fluctuate with demand, just like regular gas.

2) The 5 axes that actually matter

1. EVM compatibility: Is it bytecode-level (EVM-equivalent), language-level (Solidity/Vyper), or a distinct VM (e.g., Cairo on Starknet)? The closer to EVM equivalence, the easier migrations and tooling reuse.
2. Cost & throughput: Median swap or NFT-mint costs at typical load; behavior during spikes; batch/receipt latency; max TPS under realistic constraints.
3. Decentralization roadmap: Who runs the sequencer? Are proofs live and permissionless (optimistic fraud proofs or ZK validity proofs)? How is data availability handled? What’s the upgrade governance?
4. UX superpowers: Account abstraction (AA), paymasters (gas in tokens / sponsored gas), session keys, native bridges, and intent-based routing support.
5. Liquidity & ecosystem: CEX on/off-ramps, stablecoin depth, existing DeFi/NFT/game integrations, analytics, and wallets.

3) The L2 “Fee Stack” (mental model)

Your end-user fee ≈ (L2 execution + overhead) + (DA bytes pushed to L1 via blobs) + (L2 protocol markup, if any).

[ Your Tx ]
    │ executes on
    ▼
+------------------------+       +----------------------------+
|    L2 Execution       |       |  Data Availability (DA)    |
|  • EVM/zkVM steps     |       |  • Tx bytes -> blob (4844) |
|  • AA/paymaster hooks |  -->  |  • Compression & calldata  |
+------------------------+       |  • Blob price fluctuates   |
            │                   +----------------------------+
            ▼
      L2 Batch/Prover
            │  (ORU = fraud-window; ZK = validity proof)
            ▼
          Post to L1  -->  Fees depend on bytes posted + blob price

4) Top L2s at a glance (2025)

Note: For live metrics (TVL, UOPS, risk flags), see L2BEAT, which tracks data availability modes, stage of proofs, upgrade keys, and more.

5) Builder decision tree (choose your L2 in ~3 minutes)

Q1. Need fastest path with “works like Ethereum” bytecode?
   ├─ Yes → Prefer EVM-equivalent: Arbitrum, OP Mainnet, Base, Scroll, Linea
   └─ No → Comfortable with new VM for future perf? → Consider Starknet (Cairo)

Q2. Need shortest withdrawal delays to L1 without third-party bridges?
   ├─ Yes → ZK rollups (validity proofs): zkSync Era, Starknet, Scroll, Linea
   └─ No → Optimistic OK (fraud window) → Arbitrum, OP Mainnet, Base

Q3. Targeting retail onboarding + CEX ramps + social?
   ├─ Yes → Base (Coinbase integrations), OP Mainnet (Superchain reach)
   └─ No → Any above; weigh liquidity where your users already are

Q4. Heavy on-chain compute or high-frequency micro txs?
   ├─ Yes → Prefer ZK rollups (generally stronger latency/finality); also benchmark after 4844
   └─ No → Either family; cost often dominated by data bytes → optimize calldata

Q5. Org/tokens need conservative governance & risk tooling?
   ├─ Yes → Where audits, monitoring, and proof status are mature (Arbitrum, OP Stack family, Scroll/Linea/zkSync docs)
   └─ No → Early adopters can pick tech-forward stacks (e.g., Starknet for Cairo features)

When in doubt, run a weekend bake-off: deploy the same contract + scripts to 2–3 L2s, profile costs (swap, mint, vesting), measure time-to-inclusion, and run your failure tests (retries, congestion, MEV-sensitive txs).

6) Chain-by-chain profiles

7) Fees in practice post-EIP-4844 (examples & tuning)

After 4844, rollups pay for blob space instead of competing directly in the L1 mempool for calldata. End-user savings are substantial, but not magical: when blob demand spikes across many L2s, blob prices rise. Your fees also depend on how “chatty” your contracts are (event logs, storage writes), and how your rollup batches/compresses transactions.

1. Simple token transfer: On leading L2s, cents or sub-cents at off-peak. Your wallet’s gas panel should show the L2 execution fee and any DA component the chain exposes.
2. DEX swap: Usually low cents. Bigger during blob spikes; check chain explorers and fee dashboards before big campaigns.
3. NFT mint with metadata writes: Consider “lazy” metadata or off-chain storage with on-chain commitments to reduce bytes.
4. High-frequency updates: Batch with multicall, compress payloads, and prefer succinct events. If rollup supports it, use invoke types that minimize logs.

GAS TIPS:
• Avoid unnecessary on-chain logs (events) — they add bytes.
• Compact your structs; avoid dynamic arrays in hot paths.
• Prefer libraries that encode calldata efficiently (e.g., abi.encodePacked when safe).
• Batch user actions via multicall; aggregate small writes.
• Simulate before you ship: measure gas on two L2s at different times of day.

8) Decentralization: sequencers, proofs, DA & upgrades

Decentralization is not a single switch, it’s a set of levers. L2BEAT’s methodology tracks them rigorously. When comparing chains, ask:

• Sequencer: Is there one operator today? Is there a roadmap for shared or decentralized sequencing (e.g., Espresso, Astria, based sequencing)? What’s the fallback if the sequencer stalls?
• Proofs: For optimistic rollups: are permissionless fraud proofs live? (Arbitrum BoLD shipped in 2025.) For ZK: are proofs generated by one prover or a marketplace? Is code open and verifiable?
• Data availability: Is DA always on Ethereum (blobs), or are there optional DA layers? Pure Ethereum DA is the default for security; exotic DA may lower cost but adds risk trade-offs.
• Upgrades & admin keys: Who can upgrade the rollup contracts? Is there a timelock? Is there a security council? How are emergency shutdowns handled?

The healthiest path is gradual: ship, reduce privileged roles (proofs, sequencer, upgrades), and publish transparent timelines with measurable milestones. Check L2BEAT’s project pages for current flags and change logs.

9) Tooling, Account Abstraction, and Paymasters

Many L2s support EIP-4337 style account abstraction and paymasters. Practically, that means:

• Users without ETH can transact (gas sponsored) or pay gas in ERC-20s.
• Session keys reduce pop-ups for games and consumer flows.
• Multicall & batching are routine; AA can add spending limits and allowlists at the wallet layer.

For EVM-equivalent chains (Arbitrum, OP, Base, Scroll, Linea) the standard EVM tools work out-of-the-box. For Starknet, budget in Cairo training and pick indexers and analytics that natively support Cairo traces.

10) MEV, ordering, privacy

MEV on L2s is still MEV: ordering can influence swaps and liquidations. Some L2s provide private tx lanes or RPCs with MEV protection (simulated inclusion, encryption until sequencing). Check each chain’s docs and your RPC provider’s features. If you’re building MEV-sensitive apps, test order-flow options and document user guidance (e.g., use a private RPC for liquidations, set slippage realistically).

11) Migration & multi-chain strategy

Many teams ship on one L2, then expand. If you’re already on an OP-Stack chain (OP or Base), moving to another OP-Stack L2 is straightforward. With zkEVMs, bytecode equivalence eases portability (Scroll, Linea). For Starknet, plan parallel tracks: Cairo migration + a gateway service that lets EVM users interact while you ramp native features.

• Abstract away chain IDs from your front-end. Keep networks and RPCs in config files.
• Use a routing layer (intent routers or your own) to direct users to the cheapest/fastest path.
• Design your token strategy for multi-chain bridges (canonical + third-party) and publish risk disclosures.

12) Pre-launch checklist (copy/paste for your runbook)

[ ] Deploy contracts to 2 candidate L2s; run gas & latency profiles for 72h (peak/off-peak)
[ ] Test swaps, mints, and your heaviest function with real users on a canary
[ ] Bridge plan: canonical + fast bridge; document withdrawal times and risks
[ ] MEV plan: preferred RPCs, private lanes if needed; recommended slippage defaults
[ ] AA/paymaster: sponsor gas for first X txs; session key policy for power users
[ ] Observability: indexer choice, block explorer links, error taxonomies
[ ] Security: timelocks, multisig owners, pause roles; publish your upgrade policy
[ ] Incident response: how to disable features, revoke approvals, message users
[ ] Docs: “How to add network,” supported wallets, official links & scam warnings

13) Resources & data sources

• L2BEAT — Projects overview & risk methodology
• Ethereum.org — EIP-4844 (proto-danksharding) explainer
• Arbitrum Docs — Nitro, BoLD fraud proofs
• Optimism Docs — OP Stack, fault proofs, Superchain
• Base Docs — OP Stack chain by Coinbase
• zkSync Era Docs — Boojum, validity proofs
• Starknet Docs — Cairo, STARK proofs, AA
• Scroll Docs — zkEVM, proofs, dev guides
• Linea Docs — Consensys zkEVM

Monitor announcements and risk changes on project blogs and L2BEAT; the landscape evolves quickly.

14) FAQ

Want a bespoke L2 choice memo for your product (with fee sims and UX flows)?