A layer 1 is the base network of a blockchain. A blockchain is a shared public record of transactions that computers around the world copy and check. A layer 2 is a second network that sits on top of the layer 1 and does the day-to-day work.
The trade-off shows up when money moves back. On some layer 2s, taking it out takes about 7 days.
What is the difference between layer 1 and layer 2? A layer 1 is the blockchain itself, such as Bitcoin or Ethereum, two well-known blockchains. It keeps the official record and checks every transaction. A layer 2 is a separate network built on top of it. It handles transactions itself. It posts a record of its work to the layer 1, which keeps the official copy.
A layer 2 is designed to cost less per transaction. It packs many transactions into one entry on the layer 1, so the cost of that entry is shared.
A rollup is the most common kind of layer 2. One kind assumes each batch of transactions is correct unless someone objects within a set time. The other attaches a short piece of maths to each batch, so the layer 1 can check it at once.
Taking money back to the layer 1 takes about 7 days on OP Mainnet and about 6.4 days on Arbitrum One. OP Mainnet is the main live network of Optimism, a layer 2 project. Designs that attach the maths cut that wait to hours.
What is a layer 1 blockchain?
A layer 1 is the base network of a blockchain. According to ethereum.org, Bitcoin and Ethereum are layer 1s. Ethereum is a major blockchain that runs programs as well as payments. A layer 1 includes the computers that check transactions, the record of every transaction, and the rules for agreeing on what goes into the record.
Think of a layer 1 as a city's land registry. Its entries are final and anyone can check them.
Ethereum.org says that when demand to use Ethereum is high, the network becomes congested and transaction fees rise. On Ethereum this charge is called a gas fee. Gas is the unit that measures the computing work. The fee is the gas used times the price per unit of gas.
For how Bitcoin, Ethereum, and Solana compare, see Ethereum vs Bitcoin vs Solana. For the Ethereum network itself, see What Is Ethereum?
What is a layer 2 blockchain?
A layer 2 is a separate blockchain that extends a layer 1 and relies on its security, according to ethereum.org. It handles transactions itself, then posts the results to the layer 1. In the land registry comparison, a layer 2 is a law firm that closes hundreds of deals in its own office, then files one batch at the registry.
The most common kind is a rollup: a network that runs transactions itself, then posts the transaction data to the layer 1. Ethereum.org says a rollup packs hundreds of transactions into one transaction on the layer 1. That spreads the layer 1 fee across everyone in the batch.
The data sits on the layer 1. Ethereum.org says reversing a rollup transaction would therefore require reversing Ethereum itself.
Arbitrum One, OP Mainnet, and Base are rollups on Ethereum. A mainnet is the real, live network, as opposed to a practice network. OP is short for Optimism, the project behind OP Mainnet.
Base's docs say Coinbase built Base. Our guide to What Does Coinbase Do? covers the company.
Bitcoin has layer 2s too. Ethereum.org names the Lightning Network, a payment network built on top of Bitcoin, as one. Our guide to What Is Bitcoin? covers the base network.
Optimistic rollups vs zero-knowledge rollups
An optimistic rollup assumes every batch is correct. Anyone can object within a set time if they think a batch contains a mistake. That time is the challenge period. It works like an expense claim that gets paid unless someone flags it.
A zero-knowledge rollup attaches a proof to every batch. A proof is a short piece of maths that shows the batch was processed correctly. The layer 1 checks the proof before it accepts the batch. It works like a receipt that can be verified on the spot.
The designs differ most when money moves back to the layer 1. Finality is the point at which a transaction can no longer be reversed. The table shows the time that each network's own docs state for funds to become final on Ethereum.
Network | Design | Time stated in its docs | What the docs call it |
|---|---|---|---|
OP Mainnet | Optimistic | About 7 days | Challenge period |
Arbitrum One | Optimistic | About 6.4 days | Challenge period |
Base | Dispute window, backed by proofs | 5 days, or 1 day when two kinds of proof back the batch, plus about 20 to 60 minutes to post its record to Ethereum | Finalization window |
ZKsync chains | Zero-knowledge | About 3 hours | Finality |
Time before funds moved from the layer 2 to Ethereum are final, as each network's own documentation states it. Source: Optimism, Arbitrum, Base, and ZKsync documentation, opened 8 November 2026
In the table, the networks that wait out an objection window list days, while ZKsync lists hours. OP Mainnet and Arbitrum One are optimistic rollups. Anyone taking money back out waits about 7 days on OP Mainnet and about 6.4 days on Arbitrum One.
Base uses a window for disputes too, with proofs backing each batch.
Base's docs call it the finalization window, their name for the objection period, and give 5 days. The docs also describe a 1-day path when two separate kinds of proof back the same batch. Getting Base's latest record posted to Ethereum adds about 20 to 60 minutes on top of the window.
A withdrawal wait is a delay built in on purpose, so that objections can be made before money leaves.
ZKsync has a delay too, but a short one. Its docs list the steps, including about an hour to produce the proof. They add a delay of about 3 hours as a security measure and put full finality at around 3 hours.
What are settlement and a bridge?
Settlement is the step where the layer 1 accepts a layer 2's results as final. Ethereum.org calls Ethereum the settlement layer for zero-knowledge rollups. An optimistic rollup settles when its challenge period closes with no objection upheld, according to Arbitrum's docs.
A bridge moves coins, other digital assets, or messages between two blockchains. Ethereum.org lists the Arbitrum Bridge and the Optimism Gateway as examples.
Bridges carry their own risk. Ethereum.org says bridges account for the three biggest hacks in DeFi, meaning decentralised finance, the apps that lend and trade without a bank. A flaw in a bridge's smart contract, the program that holds the money, can expose every deposit.
What are the risks of a layer 2?
Ethereum.org says no layer 2 is as battle tested as Ethereum Mainnet. It calls many of them young and somewhat experimental.
The record is safe on Ethereum. The risk sits in the layer 2's own software and in the operators, the teams that run each layer 2 day to day.
A layer 2 therefore adds a wait to withdraw on some designs, plus extra software and operators. Its stated gain is lower fees, because many transactions share one entry on the layer 1. This guide describes how the networks work and takes no view on any coin.
A layer 1 keeps the final record, while a layer 2 does the day-to-day work and files the results with it. The cost of that arrangement is a wait to withdraw on some layer 2s and more parties to rely on.
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Common questions about layer 1 and layer 2
Is Bitcoin a layer 1 or a layer 2?
Bitcoin is a layer 1. Ethereum.org lists Bitcoin and Ethereum as layer 1 blockchains. It names the Lightning Network, a payment network built on top of Bitcoin, as a layer 2. Our guide to What Is Bitcoin? covers the base network and how it differs from Ethereum.
How long does a layer 2 withdrawal take?
It depends on the network: about 7 days from OP Mainnet, about 6.4 days from Arbitrum One, 5 days from Base (1 day when two kinds of proof back the batch), and about 3 hours on ZKsync. The first three wait out a window in which anyone can object. ZKsync is zero-knowledge. Its docs put full finality at around 3 hours, including a built-in security delay.
Is a layer 2 as secure as Ethereum?
No. A layer 2 relies on Ethereum's security for its records, but ethereum.org says no layer 2 is as battle tested as Ethereum Mainnet. Posting the data to the layer 1 means reversing a rollup transaction would require reversing Ethereum. The remaining risk sits in the layer 2's own software and operators.
Why do layer 2 networks cost less to use?
A layer 2 packs hundreds of transactions into one transaction on the layer 1, according to ethereum.org, so the fee is split across everyone in the batch. The transactions themselves run on the layer 2, away from the busy base network. Our guide to What Is Ethereum? covers gas fees.
DISCLAIMER: This article is intended for educational purposes only. Any information or analysis in this note does not constitute an offer to sell or a solicitation of an offer to buy any securities. Nothing in this note is intended to be investment advice, nor should it be relied upon to make investment decisions. Any opinions, analyses, or probabilities expressed in this note are those of the author as of the note's date of publication and are subject to change without notice.
