Knowning Layer 2 Chain

Rollup(or bundle) transactions off-chain to reduce fee and scale capacity, such as Bitcoin Lightning.

Two layer 2 rollups

Record on-chain state by writing calldata to L1(Ethereum), which more cheaper than change state on L1 chain.

Fees

Some layer 2 chain like Optimism should plus l1 fee when executing transaction on layer 1.1

Many Ethereum applications display estimated fees to users by multiplying the gas price by the gas limit. However, as discussed earlier, users on Optimism are charged both an L2 execution fee and an L1 data fee. As a result, you should display the sum of both of these fees to give users the most accurate estimate of the total cost of a transaction.

Some chain will include the fee of layer 1 to layer 2 transaction execution, such as Arbitrum2:

Tools

  1. Displaying fees to users ↩︎

  2. Estimating Gas ↩︎