Layer 2 Bridges: Complete Guide to Arbitrum, Optimism, Base & More

Layer 2 networks — Arbitrum, Optimism, Base, zkSync, Starknet, and others — have transformed Ethereum from expensive and slow into fast and affordable. But each L2 is its own separate blockchain with its own state. Moving assets between Ethereum and an L2, or between two different L2s, requires a bridge. This guide explains every option, what the trade-offs really are, and how to find the cheapest route for your specific transfer in 2026.

Why L2 Bridging Is Different from L1-to-L1 Bridging

When you bridge between two independent L1 chains (say, Ethereum to BNB Smart Chain), you are trusting a third-party bridge both ways. There is no cryptographic relationship between the two chains.

Layer 2s are different: they are cryptographically anchored to Ethereum. Every L2 posts transaction data or proofs back to Ethereum regularly. This means there is always a canonical path for moving assets — the native bridge — that inherits Ethereum's security with zero additional trust assumptions. Third-party bridges are faster and sometimes cheaper, but they add a security layer that the native bridge does not have.

Understanding this trade-off is the most important thing in L2 bridging. For more background, see our introduction to blockchain bridges and our technical explainer on how bridges work.

Native Bridges: Maximum Security, Slower Withdrawals

Every major L2 has an official native bridge maintained by the core development team. These bridges are the gold standard for security: funds are verified by the same mechanism that secures the L2 itself.

However, native bridges have a critical limitation for withdrawals (L2 → Ethereum): the challenge period.

Optimistic Rollups: Multi-Day Challenge Period

Arbitrum One, Optimism, and Base all use optimistic rollup technology. "Optimistic" means the L2 assumes transactions are valid by default and only verifies them if a fraud proof is submitted by a challenger within a fixed window. The length differs by network: Arbitrum withdrawals take at least seven days (Arbitrum docs), OP Mainnet withdrawals are completed in 7 days as a result of the withdrawal challenge period (Optimism docs), and since the Beryl upgrade Base finalizes withdrawals after a 5-day window, or 1 day on the dual-proof fast path (Base docs).

What this means practically: when you withdraw assets from Arbitrum, Optimism, or Base using the native bridge — for example moving ETH from Arbitrum back to Ethereum — you must wait out that window before your ETH or tokens arrive on Ethereum mainnet. You do not have to do anything during that time — just wait.

For deposits (Ethereum → L2, such as bridging ETH from Ethereum to Base), there is no challenge period. Deposit times differ by network: Arbitrum deposits arrive within roughly 15–30 minutes, depending on chain congestion, and OP Mainnet deposits are usually completed within 1–3 minutes.

ZK Rollups: Fast Withdrawals

ZK rollups (zkSync Era, Starknet, Polygon zkEVM, Scroll, Linea) work differently. Instead of relying on fraud proofs, they post cryptographic validity proofs to Ethereum that mathematically guarantee correctness. No challenge period needed — once a proof is verified on Ethereum, withdrawals can finalize, with timing depending on proof generation and each network’s own process.

ZK rollup native bridges do not need a multi-day challenge window, which is a significant UX advantage as ZK technology matures. Exact withdrawal times differ by network, so check each rollup’s own documentation.

Third-Party Bridges: Fast Withdrawals from Optimistic Rollups

Because the multi-day wait is impractical for most users, a thriving ecosystem of third-party bridges has emerged to provide instant liquidity. These bridges work by having liquidity providers pre-fund the destination chain and take on the wait themselves in the background.

You pay a fee for this service — you are essentially paying for someone else to wait out the withdrawal window on your behalf. The best third-party bridges for L2 routes include:

Across Protocol: Often competitive for small-to-medium EVM transfers; charges an LP fee plus a relayer fee (Across docs). Uses optimistic verification with UMA oracle. See our full Across review.
Stargate Finance: Best for large amounts ($10k+) due to unified liquidity pools. Supports non-EVM chains. See our Stargate review.
Hop Protocol: AMM-based; its quote API stopped responding in July 2026, so BridgeFees.com no longer compares Hop. See our Hop review.
Synapse Protocol: Good for routes to chains that Across does not support. See our Synapse review.

→ Compare real-time bridge fees on BridgeFees.com — no wallet needed

L2 Architecture Comparison: OP Stack vs. Arbitrum Nitro vs. ZK Rollups

The underlying technology of an L2 determines how its native bridge behaves and what security assumptions users take on.

OP Stack (Optimism, Base, Zora, Mode)

The OP Stack is an open-source L2 framework developed by Optimism. Base (Coinbase's L2), Zora, and Mode Network all run on the same codebase. Optimism’s own withdrawal challenge period is 7 days, while Base now finalizes withdrawals after 5 days (1 day on the dual-proof fast path); these chains are progressively decentralizing their proof systems. The OP Stack "Superchain" vision means these chains will eventually share sequencer economics and bridging infrastructure, making inter-OP-Stack transfers faster and cheaper.

Arbitrum Nitro

Arbitrum uses its own Nitro stack with WASM-based fraud proofs. Arbitrum One is the flagship chain. Arbitrum Nova uses a different data availability model (AnyTrust) for even lower costs, targeting gaming and social applications. Arbitrum One’s native bridge withdrawals take at least seven days.

ZK Rollups (zkSync, Starknet, Polygon zkEVM, Scroll)

ZK rollups generate cryptographic proofs of every batch of transactions. Withdrawals from the native bridge finalize as soon as the proof is verified on Ethereum — no waiting period. The trade-off is higher computational cost for proof generation, though this is dropping rapidly.

Fee Structure by Route: Major L2 Bridge Routes in 2026

The table below shows how the bridges commonly used on each route charge, as described in their own documentation. Totals change constantly with gas prices and liquidity, so compare live quotes for a current total on your transfer.

Route	Bridge	Fee structure (per docs)	Transfer time (per docs)
Ethereum → Arbitrum	Across / Native	Native: Ethereum gas only. Across: LP fee + relayer fee	Native deposits: within roughly 15–30 min, depending on chain congestion. Across: not published
Ethereum → Optimism	Across / Native	Native: Ethereum gas only. Across: LP fee + relayer fee	Native deposits: usually completed within 1–3 min. Across: not published
Ethereum → Base	Across / Native	Native: Ethereum gas only. Across: LP fee + relayer fee	Not published
Ethereum → Polygon	Across / Stargate	Across: LP fee + relayer fee. Stargate: dynamic V2 fee + LayerZero messaging fee	Not published
Arbitrum → Ethereum	Across	LP fee + relayer fee	Across: not published. Native bridge: at least seven days
Optimism → Ethereum	Across	LP fee + relayer fee	Across: not published. Native bridge: 7 days
Base → Ethereum	Across	LP fee + relayer fee	Across: not published. Native bridge: 5 days (1 day on the dual-proof fast path)
Arbitrum → Optimism	Across	LP fee + relayer fee	Not published
Arbitrum → Base	Across	LP fee + relayer fee	Not published
Optimism → Polygon	Stargate	Dynamic V2 fee + LayerZero messaging fee	Not published

Note: L2 → L2 transfers (e.g., bridging ETH from Arbitrum to Base) avoid Ethereum mainnet gas on the source side, so they are often cheaper than routes involving mainnet; compare live quotes to confirm for your route.

For detailed guides on specific routes, see:

Multi-Hop Routes: Bridging Between Two L2s

When bridging between two L2s that have no direct liquidity (e.g., a smaller L2 to another smaller L2), the cheapest route sometimes goes via an intermediate chain — a multi-hop route. For example: zkSync → Ethereum → Arbitrum may be cheaper than any direct zkSync-to-Arbitrum bridge because the direct route has thin liquidity — the second leg there is just a standard Ethereum to Arbitrum ETH deposit.

BridgeFees.com automatically finds multi-hop routes for you — it compares several bridge providers including multi-hop paths and shows the total cost so you never have to calculate this manually. Learn more about how this works in our multi-hop bridge routes explainer.

Data Sources

For up-to-date L2 TVL, bridge volumes, and security metrics, L2Beat is the most comprehensive independent resource. For a primer on L2 technology from the Ethereum Foundation, see ethereum.org/en/layer-2.

Frequently Asked Questions

Do I have to wait 7 days to withdraw from Arbitrum?

Only if you use the official Arbitrum native bridge, where withdrawals take at least seven days. Third-party bridges like Across and Stargate let you withdraw from Arbitrum without that wait by taking the wait risk themselves (for a fee). For most users, third-party bridges are the right choice for withdrawals. See our Arbitrum to Ethereum guide for details.

What is the cheapest way to bridge from Ethereum to Base?

Across Protocol is often competitive for small-to-medium transfers to Base, but check a live quote for your amount: Across charges an LP fee plus a relayer fee and publishes no fee range. With the native Base bridge you pay gas, and Base’s docs list no separate bridge fee, but withdrawals finalize after a 5-day window (1 day on the dual-proof fast path). See our full Base bridge comparison.

Are ZK rollup bridges safer than optimistic rollup bridges?

Both are considered highly secure. ZK rollup native bridges offer mathematical proof of correctness, which is arguably stronger than optimistic fraud proofs. However, ZK proofs are more complex code with more potential for implementation bugs. In practice, both have good track records. The meaningful safety difference is at the third-party bridge layer, not the native bridge layer.

Can I bridge directly between Arbitrum and Base without going through Ethereum?

Yes. Several third-party bridges (such as Across and Stargate) support direct Arbitrum → Base routes. These are generally cheaper than routing through Ethereum mainnet because you avoid mainnet gas costs. BridgeFees.com will show you whether the direct or multi-hop route is cheaper for your specific transfer.

What is the OP Stack Superchain?

The Superchain is Optimism's vision for a network of interoperable L2s all built on the OP Stack (Optimism, Base, Zora, Mode, and others). The goal is for transfers between Superchain members to be handled natively by shared infrastructure rather than third-party bridges. This is in active development as of 2026.

How does BridgeFees.com help with L2 bridging?

BridgeFees.com compares quotes from several bridge providers — including Across, Synapse, and LI.FI's aggregated routes — for all major L2 routes simultaneously. You see total cost, transfer time, and which token you will receive for each option, without connecting a wallet. It makes it easy to compare the options for any L2 transfer.