What is a layer 2?
DefinitionA layer 2 is a network built on top of a main blockchain, the layer 1, that processes transactions on its own and settles them back on that chain. On Ethereum, layer 2 networks such as Arbitrum, Optimism and Base charge far lower fees while relying on Ethereum.
How layer 2 networks work
Most Ethereum layer 2 networks are rollups. They collect many transactions, execute them off the main chain, and post the data and the result back to Ethereum. The cost of that posting is shared by many users, so each transfer costs far less.
There are two main kinds. Optimistic rollups treat each batch as valid unless someone proves otherwise during a challenge period. Zero-knowledge rollups attach a cryptographic proof that the batch is correct.
Layer 1, layer 2 and sidechains
The terms are often mixed up:
- Layer 1: a base blockchain with its own security, such as Ethereum or Bitcoin
- Layer 2: runs on top of a layer 1 and settles back to it, such as Arbitrum, Optimism and Base on Ethereum, or the Lightning Network on Bitcoin
- Sidechain: a separate chain with its own validators, connected to a main chain by a bridge; Polygon PoS is often described this way
What to watch out for
Layer 2 networks feel like Ethereum, but a few differences catch people out:
- Gas on Arbitrum, Optimism and Base is paid in ETH on that network, not on Ethereum
- Your 0x address is the same, but balances are separate: ETH on Arbitrum doesn’t show up on Ethereum
- Check that the receiver or exchange supports that exact layer 2 before you send
- Withdrawals from an optimistic rollup to Ethereum through its official bridge usually take about a week
- Many layer 2 networks still rely on a single operator, the sequencer, to order transactions
Layer 2 networks in Waletifi
Waletifi supports Arbitrum One, Optimism and Base alongside Ethereum and other EVM networks, all on the same 0x address. The network is shown on the receive and review screens, and the app warns you if you have no ETH on that network for gas.
