A Layer 2 is a secondary blockchain that sits above Ethereum, bundling many user transactions off-chain and posting the compressed result back to the main chain, which keeps Ethereum’s security while cutting fees and raising throughput. Flagship L2s include Arbitrum One, Base (incubated by Coinbase), OP Mainnet, and zkSync Era, with DefiLlama tracking on-chain activity on each. The term contrasts with Layer 1, where every transaction settles on the base chain itself.
Key Takeaways
- L2Beat data shows, as of April 2026, Ethereum Layer 2 networks secure about $41.18 billion in Total Value Secured across all rollups, validiums, and optimiums.
- L2Beat reports Arbitrum One leads with roughly $15.95 billion in Total Value Secured, followed by Base at $11.84 billion and OP Mainnet at $1.57 billion.
- The Ethereum Foundation states today’s rollups are ~5-20x cheaper than Ethereum Layer 1, and upcoming upgrades will deliver another ~100-1000x of scaling.
- Ethereum Foundation data shows the base chain averages around $0.01 per transaction, while Ethereum-backed Layer 2 networks average about $0.001, a 10x reduction passed directly to users.
- L2Beat data shows rollups represent $32.79 billion of the total, while validiums and optimiums together secure about $320.96 million, showing how dominant the rollup model is inside the broader L2 category.
How Does Layer 2 Work?
An L2 runs its own execution environment, collects user transactions inside it, then periodically hands a compressed summary of those transactions back to Ethereum, which acts as the final judge. Ethereum’s time-proven and decentralized blockchain functions as the settlement layer for other newer networks. Think of Ethereum as a single-lane toll highway and each L2 as a bus running its own route: the bus carries dozens of passengers on one paid trip through the toll, and the highway only has to verify one ticket instead of sixty.
1. Transactions are bundled off-chain
When a user sends a transaction on an L2, the network’s sequencer orders it and writes it into a rollup batch along with hundreds or thousands of others. No Ethereum block is used yet at this stage. Rollups batch transactions together and send the output to Ethereum, which is where the economics flip. The cost of posting that batch splits across every transaction inside it.
2. A state commitment is posted to Ethereum
After the batch is built, the sequencer posts a compact state commitment (a cryptographic summary of the new ledger state) to an Ethereum smart contract. Per data from L2Beat, rollups are defined as Layer 2 networks that periodically post state commitments to Ethereum, where the commitment is validated either via validity proofs or accepted optimistically and challenged via a fraud proof mechanism. The commitment plus the underlying transaction data, lets anyone reconstruct the L2 ledger independently.
3. Ethereum finalises settlement
Once Ethereum includes the commitment in a block, the batch settles. For optimistic rollups, settlement is provisional for about a week while anyone can challenge it; for ZK rollups, the validity proof settles it immediately. Either way, the L2 inherits Ethereum’s economic security without having to run its own validator set.
| Property | Ethereum Layer 1 | Ethereum Layer 2 |
| Where transactions execute | Ethereum mainnet | Off-chain, on the L2 |
| Where settlement finality lives | Ethereum mainnet | Ethereum mainnet (via state commitment) |
| Average transaction cost | ~$0.01 | ~$0.001 |
| Typical throughput | 12-20 TPS | 100s to 1,000s TPS |
| Who pays data costs | Every user | Users share the batch cost |
Sources: Ethereum Foundation, L2Beat
Why Does Layer 2 Matter?
L2 networks are the reason a swap on Ethereum no longer costs a peak-demand high-fee price. They absorbed almost all of the network’s user activity, and per the Ethereum Foundation, the protocol itself was rewritten during the Cancun-Deneb (‘Dencun’) network upgrade in March 2024 to make that split structural. Over 90% of the transaction cost users pay on rollups is due to data storage, which is why Ethereum moved that data into a new temporary ‘blob’ storage that gets deleted from Ethereum once it is no longer needed. The Dencun upgrade reconfigured the relationship between the base chain and its rollups.
EIP-4844 introduced a new transaction format for ‘blob-carrying transactions’ which contain a large amount of data that cannot be accessed by EVM execution, but whose commitment can be accessed, and targets roughly 0.375 megabytes per block compared to full sharding’s 16-megabyte target. Since Dencun shipped, rollups have begun utilizing blob storage, resulting in reduced transaction costs for users and millions of transactions processed in blobs. Across CoinLaw’s 300-plus Bitcoin and Layer-1 cluster, we’ve tracked the same pattern here: L2 dominance is not a cultural preference but a pricing change baked into Ethereum itself, and readers should expect the next round of upgrades to deepen that split rather than reverse it. The honest read is that Ethereum became an L1 designed to settle L2 data, not to compete with it.
Types of Layer 2
Not every Layer 2 uses the same proof system, and the proof system determines the security model, the withdrawal time, and the cost of running the chain. Two rollup families dominate, with a smaller validium category sitting alongside them.
Optimistic rollups
Optimistic rollups post transaction batches to Ethereum and assume they are valid unless someone proves otherwise. Optimistic rollups rely on fraud proofs: the rollup contract keeps track of its entire history of state roots and the hash of each batch, and if anyone discovers that one batch had an incorrect post-state root, they can publish a proof to the chain, proving that the batch was computed incorrectly. Optimistic rollups have lower fixed costs per batch, around 40,000 gas, but require extended withdrawal periods of approximately one week to give time for someone to publish a fraud-proof and cancel the withdrawal if it is fraudulent. Per L2Beat data, Arbitrum One and OP Mainnet are the largest optimistic rollups by Total Value Secured, at $15.95 billion and $1.57 billion.
ZK rollups
ZK rollups post a cryptographic proof with every batch, so Ethereum can verify correctness on the spot. Every ZK rollup batch includes a cryptographic proof called a ZK-SNARK, for example, using the PLONK protocol, which proves that the post-state root is the correct result of executing the batch. ZK rollups have higher fixed costs per batch, around 500,000 gas for verification of a ZK-SNARK, but enable very fast withdrawals requiring only a wait for the next batch, although ZK-SNARK proving general-purpose EVM execution is much harder than proving simple computations. zkSync Era, Starknet, Scroll, and Linea sit in this category.
Validiums and optimiums
A validium uses a ZK proof for correctness but keeps transaction data off Ethereum, which lowers cost further and weakens the data-availability guarantee. An optimium uses fraud proofs with off-chain data. Validiums and optimiums together secure about $320.96 million across Ethereum, compared to $32.79 billion in rollups, which leaves them as a tiny share of the total L2 category.
| Type | Proof mechanism | Typical withdrawal | Data availability | Example chains |
| Optimistic rollup | Fraud proofs | ~7 days | On Ethereum (calldata or blobs) | Arbitrum One, OP Mainnet, Base |
| ZK rollup | Validity proofs (ZK-SNARK / STARK) | Minutes to hours | On Ethereum | zkSync Era, Starknet, Scroll, Linea |
| Validium / Optimium | ZK or fraud proof | Varies | Off-chain (DAC or DA committee) | Immutable X, select gaming chains |
Sources: Vitalik Buterin, L2Beat
Top Layer 2 Networks by Value Secured
Four rollups hold the majority of L2 Total Value Secured, and each represents a different design bet. According to L2Beat data snapshotted in April 2026, Arbitrum One secures about $15.95 billion, Base secures about $11.84 billion, OP Mainnet secures about $1.57 billion, and Lighter secures about $742.27 million, out of $41.18 billion in total Ethereum L2 Value Secured. The gap between these three networks and the rest of the pack is wider than any comparable ranking on Layer 1.
| Layer 2 | Type | Launched | Total Value Secured (L2Beat) | DeFi TVL (DefiLlama) |
| Arbitrum One | Optimistic rollup | Aug 2021 | ~$15.95B | ~$1.98B |
| Base | Optimistic rollup (OP Stack) | Aug 2023 | ~$11.84B | ~$4.54B |
| OP Mainnet | Optimistic rollup | Dec 2021 | ~$1.57B | ~$378M |
| zkSync Era | ZK rollup | Mar 2023 | smaller tier | ~$23M |
Sources: L2Beat, DefiLlama
Arbitrum One, run by Offchain Labs, has held the number-one position by Value Secured since launch. Base is the fastest-growing among the four. Base is described in its own documentation as ‘The #1 Ethereum Layer 2, incubated by Coinbase,’ launched in August 2023, and is built on the OP Stack as one of the flagship Superchain members alongside OP Mainnet. The OP Stack itself is the standardized, shared, and open-source development stack that powers Optimism, maintained by the Optimism Collective, with Optimism Bedrock as its current iteration. The gap between L2Beat’s Total Value Secured and DefiLlama’s DeFi TVL reflects how much bridged value sits outside DeFi: L2Beat covers every bridged asset, while DefiLlama counts only smart-contract deposits.
Pros, Cons, and Risks
A Layer 2 gives users cheaper, faster transactions while borrowing most of Ethereum’s security, but the trade-offs are real and worth understanding before moving size onto one.
Advantages
- Lower fees: average Layer 2 transaction costs sit near $0.001 versus $0.01 on Ethereum mainnet, roughly a 10x reduction per transaction.
- Higher throughput: batching lifts per-second capacity from mainnet’s 12-20 TPS into the hundreds or thousands, which is what enables consumer-scale apps.
- Ethereum-level security: state commitments settle on Ethereum, so a Layer 2 inherits the economic cost of attacking Ethereum itself rather than running its own validator set.
- Composability with DeFi: every major DeFi protocol now runs native deployments on at least one Layer 2, so users can lend, swap, and stake without leaving the L2.
Trade-offs and Risks
- Withdrawal delays: optimistic rollups require about a 7-day withdrawal window, which is the fraud-proof challenge period, so withdrawing to Ethereum takes longer than depositing.
- Sequencer centralisation: most L2s currently run a single sequencer operated by the development team, which creates a censorship and liveness risk, and most roadmaps have not yet shipped a decentralised sequencer.
- Bridge risk: moving assets on and off an L2 route through a bridge contract, and historically, bridges have been among the most exploited contracts in crypto.
- Different security assumptions: a validium or optimium keeps data off Ethereum, which cuts costs but breaks the guarantee that anyone can reconstruct the ledger from Ethereum alone.
- Proof-system maturity: ZK rollup proofs for general-purpose EVM execution are newer than optimistic fraud proofs, and their code and cryptography are still being hardened in production.
Frequently Asked Questions
An L2 is a secondary blockchain that sits above Ethereum or another L1, executes transactions off the main chain, and posts compressed state data back to it. Flagship examples include Arbitrum One, Base, OP Mainnet, and zkSync Era. Per L2Beat data captured in April 2026, Ethereum Layer 2s secure about $41.18 billion across all rollups, validiums, and optimiums combined.
An L2 inherits most of its parent L1’s security through state commitments, but it adds risks that the L1 does not have. Per data from L2Beat, a rollup is defined as a Layer 2 network that periodically posts state commitments to Ethereum, validated via validity proofs or accepted optimistically and challenged via a fraud proof mechanism. Sequencer centralisation, bridge exploits, and proof-system bugs are real risks, so an L2 is broadly as safe as its design plus the bridge you used to reach it.
An optimistic rollup assumes batches are valid and lets anyone publish a fraud proof within a ~7-day window to cancel a bad batch. A ZK rollup publishes a cryptographic validity proof with every batch, so Ethereum can verify correctness on the spot. Optimistic rollups use about 40,000 gas per batch with a week-long withdrawal window, while ZK rollups use around 500,000 gas per batch but allow fast withdrawals.
Arbitrum One has the most Total Value Secured of any Ethereum Layer 2. Per data from L2Beat, Arbitrum One sits at roughly $15.95 billion in Total Value Secured, ahead of Base at $11.84 billion and OP Mainnet at $1.57 billion. Base, backed by Coinbase distribution, has been closing the gap since launching in August 2023.
Conclusion
An L2 is Ethereum’s answer to the throughput problem: keep settlement on the base chain, move execution off it, and let users pay a fraction of mainnet fees while still leaning on mainnet security. The category is already large. Per L2Beat, about $41.18 billion sits across Ethereum Layer 2 networks today, and $32.79 billion of that total is in rollups specifically, which is why Ethereum’s roadmap now treats rollups as the default deployment target rather than an optional scaling experiment.
Track our crypto coverage for protocol news, and our MetaMask wallet data coverage for how users are actually connecting to these networks in practice. The Dencun upgrade changed the economics; the next set of upgrades (full danksharding, broader fraud-proof decentralisation, and more mature ZK proving) will decide how much of Ethereum’s activity ends up living on an L2 instead of the base chain.
