Adding OP Mainnet to your centralized exchange
# Connecting to OP Mainnet
You connect to OP Mainnet the same way you do to Ethereum, by connecting to a JSON RPC endpoint.
# Endpoints
Click here for the OP Mainnet endpoints. You can choose between our public endpoints, which are rate limited, and endpoints from infrastructure providers. Given rate throughput limits, we recommend using a private rpc provider for both mainnet and testnet use cases.
# ETH balance
ETH is used precisely the way it is used in L1 Ethereum.
# Token addresses
The ERC-20 contract address for a token on OP Mainnet may be different from the address for the same token on Ethereum. The list of tokens and their addresses is here (opens new window).
For example, looking at the SNX token, we get these addresses:
| ChainID | Network | Address |
|---|---|---|
| 1 | Ethereum | 0xc011a73ee8576fb46f5e1c5751ca3b9fe0af2a6f |
| 10 | OP Mainnet | 0x8700daec35af8ff88c16bdf0418774cb3d7599b4 |
| 5 | Goerli (test network) | 0x51f44ca59b867E005e48FA573Cb8df83FC7f7597 |
| 420 | OP Goerli (test network) | 0x2E5ED97596a8368EB9E44B1f3F25B2E813845303 |
To get the total SNX balance of a user that uses OP Mainnet you need to:
- Connect to a standard Ethereum endpoint and send a
balanceOfquery to address0xc011a73ee8576fb46f5e1c5751ca3b9fe0af2a6f. - Connect to an OP Mainnet endpoint and send a
balanceOfquery to address0x8700daec35af8ff88c16bdf0418774cb3d7599b4.
# Deposits and withdrawals within OP Mainnet
The ERC-20 contracts on OP Mainnet function the same way they do on Ethereum, so you can use your existing code for withdrawals and deposits. Just connect to an OP Mainnet endpoint.
# Transaction fees
Most of the cost of an OP Mainnet transaction is not the gas consumed by the transaction itself (which is rarely above 0.001 gwei per gas), but the cost of writing the transaction in Ethereum. That cost is deducted automatically from the user's balance on OP Mainnet. If you charge your users the cost of withdrawals, you have to account for it.
You can read more about this subject here. The relevant code is here (opens new window).
# Deposits and withdrawals across chains
As a centralized exchange, there will be times that withdrawals of ETH or an ERC-20 token on either OP Mainnet or Ethereum exceed deposits and you need to transfer assets. To do that you use a bridge or a gateway. We have a standard gateway (opens new window) that receives assets on L1 (Ethereum mainnet), and mints the equivalent asset on OP Mainnet. When a user wants to withdraw the assets back to L1, the bridge burns the asset on L2 and releases it to the user on L1. If you want to use this gateway automatically, follow this tutorial for ETH (opens new window) or this one for ERC-20 tokens (opens new window).
Note that while L1 to L2 transactions typically take minutes, L2 to L1 transaction on the gateway require a seven day challenge period (opens new window).
Alternatively, you can use a third party bridge (opens new window). These bridges usually rely on liquidity pools to allow for faster withdrawals and support multiple L2 chains. However, their token selection might be more limited and they may not be as decentralized as our gateway.
When an ERC-20 token does not have an OP Mainnet equivalent you can create one. If there is no need for custom business logic, you can follow the steps in this tutorial (opens new window). If you need to implement some kind of custom logic, see this tutorial (opens new window).
# Audit reports
For a full list of audit reports visit GitHub (opens new window).