[{"data":1,"prerenderedAt":22},["ShallowReactive",2],{"blog-content-en-what-is-a-layer-2":3},{"slug":4,"title":5,"excerpt":6,"description":7,"bodyHtml":8,"faqItems":9},"what-is-a-layer-2","What Is a Layer 2? Rollups and Why L2 Fees Are So Cheap","A Layer 2 is a separate blockchain that executes off Ethereum and settles back to it, inheriting Ethereum's security while cutting fees to cents. Here is how optimistic and ZK rollups prove they are honest, why EIP-4844 blobs collapsed fees, what bridging really costs — and how WATS covers Arbitrum, Optimism and Base natively.","Layer 2 explained: how optimistic and ZK rollups execute off-chain and settle to Ethereum, why EIP-4844 blobs made fees cheap, bridging and withdrawal delays on Base, Arbitrum and Optimism, and how WATS supports those rollups natively while charging fees in ATS instead of native gas.","\u003Cblockquote>\u003Cp>A \u003Cstrong>Layer 2\u003C\u002Fstrong> is a separate blockchain that executes transactions off Ethereum and posts its transaction data and state commitments back to Ethereum, so it inherits Ethereum's security while spreading one settlement cost across thousands of batched transactions — which is why routine L2 transfers commonly cost cents rather than dollars. The dominant design is the \u003Cem>rollup\u003C\u002Fem>, in two forms: optimistic rollups (Arbitrum, Optimism, Base) treat each posted state claim as honest unless someone submits a fraud proof during a challenge window of about seven days, while ZK rollups (zkSync Era, Starknet, Scroll) attach a validity proof that Ethereum verifies before accepting the new state. Fees fell sharply in March 2024, when EIP-4844 gave rollups \u003Cem>blob space\u003C\u002Fem> — a cheap, temporary data lane with its own fee market. Your Ethereum address and keys work unchanged on the major EVM rollups: \u003Ca href=\"\u002Fhot-wallet\">WATS\u003C\u002Fa> covers Arbitrum, Optimism and Base natively alongside Ethereum, Polygon, BNB Chain, Solana and TON, and charges the fee in one token, ATS, instead of each chain's native gas coin.\u003C\u002Fp>\u003C\u002Fblockquote>\n\u003Ch2>What is a Layer 2?\u003C\u002Fh2>\n\u003Cp>A \u003Cstrong>Layer 2\u003C\u002Fstrong> is a separate blockchain that executes transactions off Ethereum but posts its data and state commitments back to Ethereum, inheriting its security. By batching thousands of transactions into one compressed record on Layer 1, an L2 keeps Ethereum's guarantees while cutting fees dramatically — often to cents. Base, Arbitrum and Optimism are the best-known examples.\u003C\u002Fp>\n\n\u003Ch2>The problem: blockspace is scarce by design\u003C\u002Fh2>\n\u003Cp>Ethereum's base layer keeps blocks deliberately small so that ordinary hardware can verify the chain — decentralization depends on it. The cost of that choice is limited throughput: when demand rises, users bid against each other for space and \u003Ca href=\"\u002Fblog\u002Fcrypto-gas-fees-explained\">gas fees\u003C\u002Fa> climb. Simply raising the limits would price out home validators and centralize the network. The scaling question was never \u003Cem>how do we make blocks bigger\u003C\u002Fem> — it was \u003Cem>how do we process more transactions without asking every node to do more work\u003C\u002Fem>. Layer 2s are Ethereum's answer.\u003C\u002Fp>\n\n\u003Ch2>How do rollups work?\u003C\u002Fh2>\n\u003Cp>A \u003Cstrong>rollup\u003C\u002Fstrong> — the dominant L2 design as of 2026 — splits the job in two. Execution happens on the rollup's own chain, where a sequencer orders transactions and runs them cheaply. The rollup then posts two things back to Ethereum: the compressed transaction data, and a claim about the resulting state. Because the data lives on L1, anyone can reconstruct the rollup's state independently — and because the state claims are checked by contracts on L1, the rollup cannot simply lie about balances. That is what \u003Cem>inheriting L1 security\u003C\u002Fem> means: your funds are ultimately protected by Ethereum, not by trusting the rollup's operator.\u003C\u002Fp>\n\n\u003Ch2>Optimistic vs ZK: how do rollups prove they're honest?\u003C\u002Fh2>\n\u003Cp>Two proving models dominate. \u003Cem>Optimistic rollups\u003C\u002Fem> — Arbitrum, Optimism, Base — assume every posted state claim is valid unless someone proves otherwise. There is a \u003Cstrong>challenge window\u003C\u002Fstrong>, typically about seven days, during which anyone with the data can submit a fraud proof showing a claim was wrong. \u003Cem>ZK rollups\u003C\u002Fem> take the opposite approach: every batch ships with a \u003Cstrong>validity proof\u003C\u002Fstrong> — a cryptographic proof that the execution was correct — which Ethereum verifies before accepting the new state. As of 2026 both models are mature; optimistic rollups host the deepest DeFi liquidity, while ZK rollups skip the challenge window entirely because their claims are proven up front.\u003C\u002Fp>\n\u003Ctable>\u003Cthead>\u003Ctr>\u003Cth>\u003C\u002Fth>\u003Cth>Optimistic rollups\u003C\u002Fth>\u003Cth>ZK rollups\u003C\u002Fth>\u003C\u002Ftr>\u003C\u002Fthead>\u003Ctbody>\u003Ctr>\u003Ctd>How claims are checked\u003C\u002Ftd>\u003Ctd>Assumed valid; fraud proofs during a challenge window\u003C\u002Ftd>\u003Ctd>Validity proof verified before acceptance\u003C\u002Ftd>\u003C\u002Ftr>\u003Ctr>\u003Ctd>Canonical withdrawal\u003C\u002Ftd>\u003Ctd>About seven days\u003C\u002Ftd>\u003Ctd>Hours, once the proof is verified\u003C\u002Ftd>\u003C\u002Ftr>\u003Ctr>\u003Ctd>Examples\u003C\u002Ftd>\u003Ctd>Arbitrum, Optimism, Base\u003C\u002Ftd>\u003Ctd>zkSync Era, Starknet, Scroll\u003C\u002Ftd>\u003C\u002Ftr>\u003C\u002Ftbody>\u003C\u002Ftable>\n\n\u003Ch2>Why are L2 fees so cheap?\u003C\u002Fh2>\n\u003Cp>Two reasons: amortization and blobs. A rollup batch spreads one L1 posting cost across thousands of transactions, so each user pays a sliver of it. But the step change came in March 2024, when \u003Cstrong>EIP-4844\u003C\u002Fstrong> gave rollups \u003Cem>blob space\u003C\u002Fem> — a dedicated data lane priced by its own fee market, built in the style of \u003Ca href=\"\u002Fblog\u002Feip-1559-explained\">EIP-1559\u003C\u002Fa> but separate from regular gas. Blobs are cheap because they are temporary: nodes keep them only for a fixed window of roughly eighteen days — comfortably past the challenge period — then prune them, so rollup data no longer competes with ordinary transactions for permanent blockspace. L2 fees collapsed almost overnight, and as of 2026 routine transfers on major rollups commonly cost cents or less.\u003C\u002Fp>\n\n\u003Ch2>What still costs money on an L2?\u003C\u002Fh2>\n\u003Cp>An L2 fee has two parts. The \u003Cem>execution fee\u003C\u002Fem> is the rollup's own gas — the same model as Ethereum, paid in ETH on Base, Arbitrum and Optimism — and it can spike when the L2 itself is congested, a popular mint being the classic case. The \u003Cem>data fee\u003C\u002Fem> is your share of the batch the rollup posts to L1, which rises when many rollups compete for blob space at once. Cheap does not mean free: the fee market moved down a layer, but it is still a market.\u003C\u002Fp>\n\n\u003Ch2>How do you move funds between L1 and L2?\u003C\u002Fh2>\n\u003Cp>You \u003Cstrong>bridge\u003C\u002Fstrong>. Deposits are simple — lock funds in the rollup's contract on L1 and they appear on the L2 within minutes. Withdrawals are where the proving models bite. From an optimistic rollup, the canonical exit waits out the challenge window — about seven days — before L1 releases funds, which is why third-party liquidity bridges exist: they front you the funds immediately for a fee and wait out the window themselves. ZK rollup withdrawals clear once the validity proof is verified on L1, typically within hours as of 2026. Either way, treat bridging as its own risk surface: prefer canonical or long-established bridges, and be skeptical of anything promising instant free exits.\u003C\u002Fp>\n\n\u003Ch2>Base, Arbitrum and Optimism: the same Ethereum, a cheaper lane\u003C\u002Fh2>\n\u003Cp>The practical magic of the major EVM rollups is how little changes for you. The address you use on Ethereum works on Base, Arbitrum and Optimism; the same signatures, the same token standards, the same EIP-1559-style gas model with ETH as the fee currency. You switch network in your wallet and everything else feels identical — just cheaper. That familiarity is why L2s absorbed so much everyday activity: swaps, mints and DeFi positions that were uneconomical on L1 make sense again. If that is where you spend your on-chain time, choosing a \u003Ca href=\"\u002Fblog\u002Fbest-wallet-for-base-and-arbitrum-defi\">wallet that handles Base and Arbitrum DeFi well\u003C\u002Fa> matters more than any single fee saving.\u003C\u002Fp>\n\n\u003Ch2>How WATS fits in\u003C\u002Fh2>\n\u003Cp>WATS supports the major EVM rollups natively: Arbitrum, Optimism and Base sit in the same wallet as Ethereum, Polygon and BNB Chain — one EVM address, one set of keys across all of them — alongside Solana and TON, so moving between L1 and an L2 is a network switch rather than a new setup. WATS is fully non-custodial throughout — you hold your keys, and WATS never holds a key.\u003C\u002Fp>\n\u003Cp>It also removes the per-rollup gas float. In the \u003Ca href=\"\u002Fhot-wallet\">WATS Hot Wallet\u003C\u002Fa> the network fee for a transaction is charged in one token, \u003Cstrong>ATS\u003C\u002Fstrong>, instead of the chain's native gas: on EVM networks, Layer 2s included, via an \u003Ca href=\"\u002Fblog\u002Fwhat-is-a-paymaster\">ERC-4337 paymaster\u003C\u002Fa>, and on Solana and TON via an equivalent fee-payer\u002Frelayer. ATS is a LayerZero OFT, so a single balance covers fees across all of them, and collected ATS is burned from a 100M supply toward a 30M floor. It is not a discount, for the reason described above: the rollup's execution and data costs are still settled underneath, and only the token you spend changes. WATS is the first and only wallet to combine ERC-4337 + OFT single-token fees, charged instead of native gas, with that burn — details on the \u003Ca href=\"\u002Fats-fee\">ATS fee page\u003C\u002Fa>.\u003C\u002Fp>\n\u003Cp>So if most of your on-chain activity has already moved to Base, Arbitrum and Optimism, the concrete step that follows from all of the above is to stop maintaining a separate ETH float on each rollup and a separate wallet setup per chain: keep one ATS balance in the WATS Hot Wallet, let it settle each rollup's gas in the background, and keep the keys in your own hands while you do it.\u003C\u002Fp>",[10,13,16,19],{"q":11,"a":12},"Is a Layer 2 as secure as Ethereum itself?","Rollups inherit Ethereum's security for data and settlement: transaction data is posted to L1, and state claims are checked by fraud or validity proofs, so an operator cannot fake balances. What differs is operational trust — most rollups still run centralized sequencers and retain upgrade keys as of 2026, so censorship-resistance and governance are weaker than L1's. Your funds are protected by Ethereum; day-to-day liveness depends on the rollup.",{"q":14,"a":15},"Why do withdrawals from Arbitrum or Optimism take about a week?","Optimistic rollups assume posted state claims are honest and give challengers roughly seven days to submit a fraud proof before Ethereum treats a claim as final. A canonical withdrawal must wait out that window so a fraudulent claim can be caught and thrown out before any funds leave. Third-party liquidity bridges shortcut the wait by fronting you funds on L1 for a fee and claiming the withdrawal themselves later — convenient, but an extra party to trust.",{"q":17,"a":18},"Do I need a new wallet or address to use a Layer 2?","No. Major EVM rollups like Base, Arbitrum and Optimism use the same accounts as Ethereum: your existing address and private key work unchanged, and you simply switch networks in your wallet. Gas is paid in ETH on that network, so you need a small balance bridged there first. The one real difference is the bridge itself — moving funds between L1 and L2 is a separate transaction with its own fees and, on exits, delays.",{"q":20,"a":21},"Which wallet works across Ethereum and its Layer 2s?","WATS covers Ethereum, Arbitrum, Optimism and Base natively — the same address and the same keys on each — alongside Polygon, BNB Chain, Solana and TON, so moving onto a rollup is a network switch rather than a new wallet. It also removes the per-rollup gas float: in the WATS Hot Wallet a transaction's network fee is charged in a single token, ATS, using an ERC-4337 paymaster on EVM networks including those L2s and an equivalent fee-payer on Solana and TON. That changes which token pays, not what the transaction costs — the rollup's execution and data fees are still settled underneath. WATS is fully non-custodial: you hold your keys, and WATS never holds a key.",1786059328072]