Blockchain API
Mainnet + Sepolia
Optimism API
The Crypto APIs Optimism API, part of the Blockchain API, lets you read balances, token transfers and blocks on Optimism and send transactions without running a node. One API key covers mainnet and sepolia. Webhooks tell your server when a payment confirms, and we never hold your private keys.
What can you do with the Optimism API?
Read balances and history
Confirmed balances and transactions for any Optimism address, and blocks.
Work with tokens
Read or prepare Optimism token transfers through the same API.
Estimate fees
Fee recommendations for slow, standard and fast confirmation on Optimism.
Prepare and broadcast
We build the unsigned transaction. You sign it, and we send it to the network.
Get webhooks
We call your URL when coins arrive at an address and when the transaction confirms.
Same shape on 35+ networks
Swap optimism for another chain in the path, such as Arbitrum or Base.
How do I get the latest Optimism block?
Send one GET request with your API key; the same request works on sepolia when you replace mainnet with sepolia in the path.
- Base URL
https://rest.cryptoapis.io - Auth: the X-API-Key header
- JSON responses, same shape on every chain
curl https://rest.cryptoapis.io/blocks/evm/optimism/mainnet/latest/details \ -H "X-API-Key: YOUR_API_KEY"
const res = await fetch( "https://rest.cryptoapis.io/blocks/evm/optimism/mainnet/latest/details", { headers: { "X-API-Key": process.env.CRYPTOAPIS_KEY } }, ); const { data } = await res.json(); console.log(data.item);
import os, requests r = requests.get( "https://rest.cryptoapis.io/blocks/evm/optimism/mainnet/latest/details", headers={"X-API-Key": os.environ["CRYPTOAPIS_KEY"]}, ) print(r.json()["data"]["item"])
{
"height": 234324,
"hash": "0x6b1fdd6357845016fb238d1bd58992a01b01c94e668f55e9502d65f0a50ac021",
"transactionsCount": 23432,
"timestamp": 1681893875
}
Which Optimism endpoints are available?
The main calls. Every path takes the network: mainnet or sepolia.
/addresses-latest/evm/optimism/mainnet/{address}/tokens-transfers/blockchain-events/optimism/mainnet/address-coins-transactions-confirmedHow do I send a Optimism transaction without giving up my keys?
Crypto APIs never holds your private keys. You keep signing; we do the rest.
- Step 1 Prepare We build the unsigned transaction with the fee set.
- Step 2 Sign locally You sign on your own servers. Keys never leave.
- Step 3 Broadcast We push the signed transaction to the Optimism network.
- Step 4 Confirm A webhook tells you when it confirms.
Optimism API vs Optimism RPC: which do I need?
Most apps start with the API. Use RPC when you need a method the node exposes directly.
Optimism RPC
Need raw node calls (JSON-RPC)? NodeGrid RPC will give you one endpoint with automatic failover between partner providers. Until then, JSON-RPC access is part of the Blockchain API.
Explore NodeGrid RPCCheck a Optimism address for AML risk
A free risk band and sanctions check for any Optimism address is coming soon. Today, screen addresses with the AML API.
Coming soonThe Optimism Blockchain
Optimism is a Layer-2 scaling solution for Ethereum, aiming to improve transaction throughput and reduce fees by employing optimistic rollups, a technology that enables faster and more cost-effective smart contract execution.
Optimism blockchain, crafted by Ethereum developers for Ethereum developers, stands as a swift, reliable, and scalable Layer 2 blockchain. Functioning as a streamlined augmentation to current Ethereum software, Optimism architecture mirrors the EVM, ensuring seamless scalability for your Ethereum applications. If a feature operates on Ethereum, it seamlessly translates to OP Mainnet, offering the same functionality at a significantly reduced cost.
Other EVM chains, same request shape
Optimism API questions
Is there a free Optimism API?
You can try it free for 14 days. The Blockchain API free trial covers Optimism and every feature, with no card. It ends after 14 days or when its credits run out; after that, calls need a subscription, listed on the pricing page.
How do I get the balance of a Optimism address?
Call the address balance endpoint with the address; it returns the confirmed ETH balance. Token balances live in the token contracts, so list the address's token transfers to see them.
How do I broadcast a Optimism transaction?
Sign the transaction on your own server, then send the signed raw transaction to the broadcast endpoint, authenticated with your API key, and Crypto APIs pushes it to the Optimism network and returns the transaction ID. We can prepare the unsigned transaction for you first.
Do you support Optimism sepolia?
Yes. Every Optimism endpoint works on mainnet and sepolia. Change mainnet to sepolia in the path; the same API key works on both.
What makes Optimism different to work with?
It is an account-model EVM chain — every address has a single balance and a nonce. Tokens live in their own contracts rather than in the account balance, so reading them means calling the token contract; and every transaction needs the account's next nonce, which the same API returns.
How do I know when a Optimism transaction is confirmed?
Create a webhook subscription for the address. Crypto APIs calls your URL when a transaction to or from it confirms on Optimism.
Start building on Optimism today
14-day free trial, mainnet included. No card needed.