6.4[Advanced Topics & DeFi](https://wealtii.com/learn) # Layer 2 Solutions Explained: Rollups, Lightning & Fees By [Zayd Ahmed](https://wealtii.com/editorial-policy#zayd-ahmed), Founder & CEO, Wealtii · Published 12 February 2026 · Last reviewed 21 October 2026 **Layer 2 (L2) solutions** are networks built on top of a base blockchain such as Ethereum or Bitcoin. They process transactions off the main chain and then settle or prove the results on it, which makes transactions cheaper and faster. How much of the base chain's security an L2 inherits depends on its design. ## Why do blockchains need layer 2 networks? Base-layer blockchains limit how many transactions fit in each block so that ordinary computers can still verify the chain. That protects decentralisation and security, but when demand rises users bid against each other for block space and fees climb. This trade-off is known as the [blockchain scalability trilemma](https://wealtii.com/learn/blockchain-scalability-trilemma). Layer 2 networks move most of the computation off the base chain and use it only for settlement and data, so many transactions share the cost of one base-layer transaction. Our comparison of [layer 1 vs layer 2 blockchains](https://wealtii.com/learn/layer-1-vs-layer-2) covers the base-layer side. ## What are the main types of layer 2? | Type | How it works | Examples | Withdrawal to the base chain | | --- | --- | --- | --- | | Optimistic rollups | Post transaction data to Ethereum and assume it is valid; anyone can challenge a wrong batch with a fraud proof during a challenge window | Arbitrum One, OP Mainnet, Base | About a week via the official bridge (6.4-day challenge period on Arbitrum One) | | ZK (validity) rollups | Post data plus a cryptographic validity proof that the batch was executed correctly | zkSync Era, Starknet, Linea, Scroll | Once the proof is verified on Ethereum; timing varies by network | | Payment channels | Two parties lock funds on-chain and exchange signed updates off-chain; only opening and closing are recorded on the base chain | Bitcoin Lightning Network | When the channel is closed | | Validiums and other designs | Use validity proofs but keep transaction data off Ethereum, which lowers cost but weakens guarantees | Varies | Depends on the operator and data committee | Sidechains such as Polygon PoS are often grouped with layer 2s, but they run their own validators and do not rely on Ethereum to verify their transactions, so they carry different security assumptions. ## How does a rollup process a transaction? 1. **Submission:** you sign a transaction in a normal wallet connected to the rollup. 2. **Sequencing:** a sequencer orders and executes transactions and gives you a fast "soft" confirmation, usually within seconds. 3. **Batching:** the rollup compresses many transactions and posts the data to Ethereum. 4. **Verification:** an optimistic rollup waits out its challenge window; a ZK rollup has its validity proof checked by an Ethereum smart contract. 5. **Finality:** once that step completes, the rollup's state is settled on Ethereum and withdrawals through the official bridge can be completed. ## How have Ethereum upgrades lowered layer 2 fees? The Dencun upgrade in March 2024 introduced proto-danksharding (EIP-4844). It gave rollups "blobs", a cheaper data space than ordinary transaction data, which Ethereum nodes delete after about 18 days. Rollups passed much of that saving on to users. The Fusaka upgrade, activated on 3 December 2025, added PeerDAS, which lets nodes check blob data by sampling instead of downloading every blob, so the network can carry more rollup data. ## What are the risks of using layer 2 networks? - **Centralised sequencers:** most rollups run a single sequencer that could delay or censor transactions, although mature designs let users force transactions through Ethereum. - **Upgrade keys:** a team or security council can often change the rollup's contracts. L2BEAT's "stages" framework rates how far each rollup has reduced this control; on 21 October 2026 it listed Arbitrum One, Base and OP Mainnet at Stage 1. - **Bridge risk:** bridges hold large pools of locked assets and have been frequent targets for hacks. - **Withdrawal delays:** leaving an optimistic rollup through its official bridge takes about a week. - **Wrong-network mistakes:** sending tokens on the wrong network can make them hard or impossible to recover. ## How do you start using a layer 2? Many exchanges let you withdraw directly to popular layer 2 networks, which avoids paying base-layer fees for bridging. Otherwise, use the rollup's official bridge from its documented website. Add the network to your wallet from an official source, keep a little ETH on the L2 for gas, and send a small test amount first. Our guide to [setting up a crypto wallet](https://wealtii.com/learn/how-to-set-up-a-crypto-wallet) covers network settings and seed phrase backups. ## What does layer 2 growth mean for investors? Layer 2 networks pay Ethereum for the data they post, so their activity creates some demand for ETH block space. Since blobs made that data cheap, how much value flows back to ETH holders is debated, and investors should not assume L2 growth automatically lifts the price of ETH. Wealtii's [Digital Asset Core Index Fund](https://wealtii.com/funds/wealtii-digital-asset-core-index-fund) holds ETH as one of seven crypto assets (12.1% target allocation). Wealtii itself operates on BNB Smart Chain, a separate layer 1, and is not regulated. ## Frequently Asked Questions ### What is a layer 2 in crypto? A layer 2 is a network that runs on top of a base blockchain (layer 1) such as Ethereum or Bitcoin. It processes transactions off the main chain and then posts data or proofs back to it, which makes transactions cheaper and faster while relying on the base chain for settlement and, depending on the design, security. ### What is the difference between optimistic and ZK rollups? Optimistic rollups assume batches are valid and give anyone a challenge window to submit a fraud proof, which is why withdrawals to Ethereum through their official bridges take about a week. ZK rollups attach a cryptographic validity proof to each batch, so funds can be withdrawn once the proof is verified on Ethereum. ### Why do withdrawals from some layer 2 networks take a week? Optimistic rollups such as Arbitrum One and OP Mainnet must wait for their challenge period to end before a withdrawal to Ethereum is final. Arbitrum’s documentation gives a challenge period of 6.4 days. Third-party bridges can be faster but add their own risks and fees. ### Is BNB Smart Chain a layer 2? No. BNB Smart Chain is a separate EVM-compatible layer-1 blockchain with its own validator set. It does not inherit Ethereum’s security, although many of the same wallets and tools work on both networks. ## Sources & References 1. [ethereum.org — Layer 2 networks](https://ethereum.org/en/layer-2/) (accessed 21 Oct 2026) 2. [ethereum.org — Danksharding and proto-danksharding (EIP-4844)](https://ethereum.org/en/roadmap/danksharding/) (accessed 21 Oct 2026) 3. [Ethereum Foundation blog — Fusaka mainnet announcement (6 Nov 2025)](https://blog.ethereum.org/2025/11/06/fusaka-mainnet-announcement) (accessed 21 Oct 2026) 4. [Arbitrum documentation — How the optimistic rollup works (challenge period)](https://docs.arbitrum.io/how-arbitrum-works/optimistic-rollup) (accessed 21 Oct 2026) 5. [L2BEAT — Rollup stages framework and project risk ratings](https://l2beat.com/stages) (accessed 21 Oct 2026) Disclaimer: Educational content only, not financial advice. Network designs, risk ratings and fees change frequently, and digital assets are volatile. Wealtii is early-stage and is not regulated by any financial regulator. ## Further reading from official sources - [NIST: Blockchain Technology Overview](https://csrc.nist.gov/pubs/ir/8202/final) - [Bitcoin white paper](https://bitcoin.org/bitcoin.pdf) [Zayd Ahmed](https://wealtii.com/editorial-policy#zayd-ahmed) Founder & CEO, Wealtii Computer Science Engineer | 5+ Years in DeFi & Digital Assets