OP Mainnet
Optimistic rollup on Ethereum and reference chain of the open-source OP Stack.
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OP Mainnet key facts
| Category | Layer 2 network |
|---|---|
| Chains | Ethereum L2 |
| Platforms | Web, API |
| Fees | Execution gas fee plus L1 data fee plus operator fee (after Isthmus) |
| Open source | Yes, MIT license (github.com/ethereum-optimism/optimism) |
| Token | OP (governance, Token House voting) |
What is OP Mainnet?
OP Mainnet is an optimistic rollup on Ethereum built with the OP Stack. Fees are an execution gas fee, an L1 data fee and, since the Isthmus upgrade, an operator fee. Transactions finalize in about 15 to 30 minutes, but Standard Bridge withdrawals wait 7 days for fault proofs.
How OP Mainnet works
OP Mainnet is EVM equivalent: a transaction that uses 100,000 gas on Ethereum uses 100,000 gas on OP Mainnet, just at a lower price.
The sequencer orders transactions by priority fee, and the chain posts transaction data to Ethereum, as blobs where enabled. That is where the L1 data fee comes from. It depends on the compressed size of your transaction and the current Ethereum base fee and blob gas price.
Leaving for Ethereum takes three transactions. You start the withdrawal on L2. After a state proposal covering your block reaches the DisputeGameFactory, you prove the withdrawal on L1 against it. Once the 7-day fault challenge period has passed and the dispute game resolves in the proposal's favor, you finalize it on L1. Anyone can post or challenge proposals.
How to start with OP Mainnet
- Add OP Mainnet to your wallet: chain ID 10, currency ETH, public RPC mainnet.optimism.io, explorer explorer.optimism.io.
- The public RPC is rate limited and has no websocket support, so heavy users need their own node or a paid provider.
- Gas is paid in ETH.
- Because gas usage matches Ethereum, you can estimate costs with the same tools.
- For faster inclusion, the docs point to eth_maxPriorityFeePerGas to pick a priority fee.
OP Mainnet fees and limits
Before the Isthmus upgrade, the total fee was gas used times base fee plus priority fee, plus the L1 data fee. After Isthmus, an operator fee is added on top. The base fee works like Ethereum's EIP-1559 base fee, with parameters tuned for shorter blocks. The priority fee can be zero, but some wallets and Geth set a 1 gwei default minimum. The L1 data fee is charged automatically to the sender of every transaction.
Risks to know before using OP Mainnet
- Optimism's docs say OP Stack chains depend on a 2-of-2 multisig.
- One side is a 10-of-13 Optimism Security Council multisig and the other is a 5-of-7 Optimism Foundation multisig.
- Together they can upgrade core contracts with no delay.
- The Council also acts as Guardian: it can block invalid proposals and switch to a permissioned dispute game.
- The Foundation runs the only sequencer, though users can bypass it through the OptimismPortal contract.
- The docs also warn that unknown bugs could cause loss of funds.
OP Mainnet alternatives
Other projects people compare with OP Mainnet.
Gaming-focused Ethereum layer 2 on the OP Stack, launched by Sky Mavis, with RON as its gas and staking token.
Validity rollup on Ethereum using STARK proofs and the Cairo language, with fees paid in STRK.
ZK rollup on Ethereum that proves every operation with zero-knowledge proofs, with its own EraVM.
Optimistic rollup on Ethereum (Arbitrum One) built on the Offchain Labs Nitro stack, governed by ARB holders.
Ethereum layer 2 network built by Coinbase, with no native token and ETH used for gas.
zkEVM rollup on Ethereum incubated within Consensys, with ETH for gas and a LINEA burn token.
Where OP Mainnet ranks on DappAtlas
OP Mainnet pros and cons
- Transactions finalize on Ethereum in about 15 to 30 minutes
- OP Stack code is public under the MIT license
- Forced inclusion from L1 if the Sequencer goes down
- Standard Bridge withdrawals are delayed 7 days
- Soft finality relies on a single Sequencer run by the chain operator
- Extra operator fee component after the Isthmus upgrade
OP Mainnet FAQ
What is OP Mainnet?
OP Mainnet is an optimistic rollup on Ethereum built with the OP Stack. Fees are an execution gas fee, an L1 data fee and, since the Isthmus upgrade, an operator fee. Transactions finalize in about 15 to 30 minutes, but Standard Bridge withdrawals wait 7 days for fault proofs.
Which chains does OP Mainnet support?
Ethereum L2.
How much does OP Mainnet cost?
Execution gas fee plus L1 data fee plus operator fee (after Isthmus), according to OP Mainnet’s own page (checked Sep 26, 2026).
Sources
How this page works
Sources: OP Mainnet: official site, OP: Transaction fees on OP Mainnet, OP: GitHub repository. Data as of Oct 1, 2026.
Not affiliated with any project listed. Educational content, not financial advice.