optimism_outputAtBlock

Returns the OP Stack output-root data for a MegaETH block.

Summary

Returns the same output-root data as mega_outputAtBlock. The two names are aliases on MegaETH.

The public MegaETH endpoint supports this method. The standard, node, and gateway layers below identify behavior that differs from a generic Ethereum endpoint.

Parameters

Position	Name	Type	Required	Description
0	blockNumber	QUANTITY	Yes	Concrete hexadecimal block number; block tags are not accepted.

Result

An output object containing outputRoot, blockRef, withdrawalStorageRoot, stateRoot, and syncStatus. The upstream version field can be present on a fresh response but is omitted by the gateway's cached projection. See mega_outputAtBlock for every field.

Comparison with Ethereum Standard JSON-RPC

Ethereum Standard

optimism_outputAtBlock is not part of the core Ethereum execution JSON-RPC API. It is an OP Stack extension.

MegaETH Node Behavior

This is the OP node's native output-root method. The related MegaETH execution-node method is mega_optimismOutputAtBlock, which forwards to it.

MegaETH Public Gateway

The gateway accepts this name and mega_outputAtBlock, routes both to the OP-node pool as optimism_outputAtBlock, and applies the same split cache policy for output data and synchronization status. Because the cached projection omits version, callers must not require that field even though it can appear on a fresh response.

Errors

The | Scope | column distinguishes method failures from gateway policy errors.

No method-specific errors were observed.

Code	Scope	Message	When it happens
-32005	Transport/policy	Rate limit exceeded	The caller exceeds the public gateway's simple read budget.
-32099	Transport/policy	Payload too large	The request body exceeds the 128 KiB public endpoint limit.

See also Error Codes.

Examples

Endpoint: https://mainnet.megaeth.com/rpc

Capture date: July 27, 2026

Outcome: success

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "optimism_outputAtBlock",
  "params": ["0x154de48"]
}

The captured response below is abridged; syncStatus contains additional L1 and L2 progress fields.

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": {
    "version": "0x0000000000000000000000000000000000000000000000000000000000000000",
    "outputRoot": "0xf90851c88ec4adfe04b03f33beab99bbabbd73fc474ab7b3a8fa109a3913f047",
    "blockRef": {
      "hash": "0xce5344be15fecbe70574c97e57626f79a0816e8ebfc37a53ad535e82dd2def56",
      "number": 22339144
    },
    "withdrawalStorageRoot": "0x891f4462376be7ecac17a67a0ee5be7bc0c35979c182e5f7f19ebb2b1e320cc3",
    "stateRoot": "0x686f5150a2aec8f1b5ae15108288530860fa4157a9f39c71e55b0fa24783d506",
    "syncStatus": {
      "head_l1": {
        "number": 25622556
      }
    }
  }
}

Sources

• Spec: EIP-1474 for JSON-RPC framing and error conventions; this method is an extension or legacy compatibility method.
• Code: [email protected]:megaeth-labs/mega-reth.git @ ab60376631228edab3a6df180f295280bad26e93: crates/megaeth/rpc/src/mega.rs
• Code: [email protected]:megaeth-labs/mega-rpc.git @ 06aa35aa95d569c227cc25d2aa12834eb0458aa0: workers/src/processors/op-output-processor.ts
• Probe: MegaETH Mainnet public endpoint, July 27, 2026; response abridged to stable top-level fields