Think of the base chain as a courthouse that records final judgements. It is deliberately slow and expensive because every full node has to check everything. Block space on a busy <a href="/glossary/layer-1/">layer 1</a> is scarce, so when demand rises, fees rise with it. A layer 2 handles the day-to-day traffic and files a summary with the courthouse instead of asking it to hear every case.
Rollups are the dominant approach. They batch hundreds or thousands of transactions, execute them off-chain, then post compressed data back to layer 1 along with something that lets anyone confirm the result. Optimistic rollups assume the batch is valid and open a challenge window in which anyone can submit a fraud proof, which is why withdrawals to the base chain can take a while. Validity rollups, including <a href="/glossary/zk-rollup/">zk-rollups</a>, publish a cryptographic proof of correctness instead, so there is no waiting period to dispute.
The honest caveats matter. Moving funds between layers means crossing a <a href="/glossary/bridge/">bridge</a>, and bridge contracts have been a repeated target for very large thefts. Many layer 2s also run a single sequencer that decides transaction ordering, which is a centralisation point; escape hatches usually exist on paper but are rarely tested by ordinary users. Assets sitting on a layer 2 are a claim redeemable on the base chain, not the same object as a base-chain coin.
One practical trap: the same address often exists on several networks, so a transfer sent to the correct address on the wrong network can be extremely difficult or impossible to recover. Check the network selector, not just the address, before you confirm anything.
Key takeaways
- A layer 2 inherits much of the base chain's security but adds its own assumptions, usually a bridge and often a single sequencer.
- Optimistic rollups make base-chain withdrawals wait out a challenge window; validity-proof rollups do not.
- Sending funds to the right address on the wrong network is one of the most common and least recoverable mistakes in crypto.
Layer 2 — frequently asked questions
Is a layer 2 as safe as the chain it sits on?
Not identically. A well-designed rollup lets anyone reconstruct its state from data published on the base chain, which is a strong guarantee. But you are also trusting the bridge contract, the proof system, and often a single sequencer for ordering and liveness. The realistic summary is that a good layer 2 is close to base-chain security for settlement, with extra risks around access and timing.
Why are fees so much lower on a layer 2?
Because the cost of using scarce base-chain block space is shared. A rollup packs many transactions into one batch and posts a compressed record of them, so each user pays a small slice of that single settlement cost rather than the full price of their own base-chain transaction. Execution also happens on cheaper infrastructure rather than being replayed by every node on the main chain.
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