The Optimism chain ID is 10 (0xa in hex). OP Mainnet, formerly called Optimism, is an optimistic rollup on Ethereum and the first chain of the OP Stack. Gas is paid in ETH. Below are the exact settings MetaMask asks for, public RPC endpoints we tested on October 27, 2026, and a one-click button to add the network.
Optimism Network Details for MetaMask
| Field | Value |
|---|---|
| Network name | OP Mainnet |
| RPC URL | https://mainnet.optimism.io |
| Chain ID | 10 |
| Currency symbol | ETH |
| Block explorer | https://optimistic.etherscan.io |
Copy these values exactly. If the RPC URL returns a different chain ID than the one you enter, MetaMask stops with a chain ID mismatch warning: that usually means a typo or an RPC for another network.
Optimism RPC URLs (Tested October 27, 2026)
| RPC endpoint | Returned chain ID | Response time |
|---|---|---|
https://mainnet.optimism.io | 10 | 245 ms |
https://optimism.drpc.org | 10 | 177 ms |
https://optimism-rpc.publicnode.com | 10 | 184 ms |
https://optimism-rpc.blockreq.com/v1/rpc/public | 10 | 186 ms |
https://optimism.gateway.tenderly.co | 10 | 332 ms |
We sent eth_chainId and eth_blockNumber to each endpoint from Europe on October 27, 2026; the table lists only endpoints that answered with chain ID 10. The latest block was 158,756,755. Public endpoints are free and rate limited: for an app or a bot, use a paid provider or your own node.
How to Add Optimism to MetaMask
- Click Add Optimism to MetaMask above, or open MetaMask and go to Networks → Add a custom network.
- Enter the network name OP Mainnet, RPC URL
https://mainnet.optimism.ioand chain ID 10. - Set the currency symbol to ETH and the block explorer to https://optimistic.etherscan.io.
- Save and switch to the new network. Your 0x address is the same as on other EVM networks.
Tip: The network is listed as OP Mainnet in most wallets now; it is the same network as “Optimism” with chain ID 10.
OP Sepolia Testnet
| Field | Value |
|---|---|
| Network name | OP Sepolia |
| RPC URL | https://sepolia.optimism.io |
| Chain ID | 11155420 (0xaa37dc) |
| Currency symbol | ETH |
| Block explorer | https://sepolia-optimism.etherscan.io |
Testnet tokens come from faucets and are worth nothing. Do not send real ETH to a wallet connected to OP Sepolia.
How to Get ETH on Optimism
The widget at the top of this page is set to swap into ETH on Optimism: pick the token you have on another network, enter your address and sign once. Routes, fees and timing are covered in our Optimism bridge guide.
Related
- What is a chain ID? - how chain IDs protect transactions
- How to add a network to MetaMask - the manual steps in detail
- Gas tokens by chain - what each network charges fees in
- All networks: chain ID list