API Reference

The OP Stack exposes three distinct surfaces: the execution RPC (op-geth, standard Ethereum JSON-RPC), the consensus/rollup RPC (op-node and the operator services), and the on-chain interfaces (the Solidity contracts on L1). Most application developers only use the first; operators and infrastructure builders use all three.

Execution RPC (op-geth)

Identical to go-ethereum for standard operations:

• eth_blockNumber, eth_getBlockByNumber/Hash, eth_getTransactionByHash, eth_getTransactionReceipt
• eth_call, eth_estimateGas, eth_sendRawTransaction, eth_getBalance, eth_getCode, eth_getStorageAt
• eth_getLogs, eth_getProof (for merkle-proof based tooling)
• Standard net_, web3_, and admin_ namespaces

Rollup RPC (op-node)

• optimism_syncStatus — the canonical head, safe head, unsafe head, current L1, and the sync stage. The single most useful health/debug endpoint.
• optimism_outputAtBlock(blockNumber) — returns the output root for an L2 block, the basis for proving withdrawals.
• optimism_rollupConfig — the chain's full rollup configuration (contracts, genesis, channel timeouts, etc.).
• rollup_getPayload, rollup_derivePayloadAttributes — internal payload plumbing used by node operators.

Operator admin RPC

• optimism_batcher_channelState, optimism_batcher_forceSubmitChannel — on op-batcher's separate admin port.
• optimism_proposer_outputL2Block, optimism_proposer_outputRoot — on op-proposer's admin port.
• admin_nodeInfo, admin_peers — P2P diagnostics on op-node.

Engine API (op-node ↔ op-geth)

Not something application developers call, but the protocol heart: engine_forkchoiceUpdated, engine_newPayload, engine_getPayload (and the V3/V4 blob-capable variants), engine_exchangeCapabilities. The engine's rollup PayloadAttributes carry the L1 origin and forced deposits.

Key on-chain interfaces

• OptimismPortal — depositTransaction, proveWithdrawalTransaction, finalizeWithdrawalTransaction, depositTransactionCount.
• CrossDomainMessenger — sendMessage, relayMessage, messageNonce, failedMessages (for replayable failed relays).
• L1StandardBridge — depositETH, depositERC20, finalizeETHWithdrawal, finalizeERC20Withdrawal.
• SystemConfig — batcherHash, overhead, scalar, gasLimit, setSystemConfig.
• DisputeGameFactory — create, gameAtIndex, gameCount.
• L2 predeploys — L2ToL1MessagePasser, L1Block, L2StandardBridge, GasPriceOracle, WETH9, at deterministic addresses.

Edge cases

• optimism_syncStatus shows three heads — tools must decide which to trust. For anything with financial impact, use the safe head, not the unsafe head.
• The rollup config differs per chain (different contract addresses, batch inbox, chain ID). Never hardcode it; read it from optimism_rollupConfig or the Superchain Registry.
• GasPriceOracle's getL1Fee/getL1GasUsed return values in wei on the L2 using the current L1 basefee; they are estimates, and the actual fee is computed at execution time.