mega_getBlockWitness

mega_getBlockWitness JSON-RPC reference for MegaETH.

Summary

Returns the execution witness for a block.

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

Parameters

keys object REQUIRED

Block lookup key.

• blockNumber Quantity REQUIRED

  Target block number.
• blockHash Hash32

  Block hash for the same block number. Always include it when available so the lookup is pinned to a specific fork.
• parentHash Hash32

  Parent block hash for an OP payload lookup. Must be supplied together with attributesHash and cannot be combined with blockHash.
• attributesHash Hash32

  Payload-attributes hash for an OP payload lookup. Must be supplied together with parentHash and cannot be combined with blockHash.

A blockNumber-only lookup returns the first stored witness at that height and is not reorg-safe. Use blockNumber together with blockHash, or the paired parentHash and attributesHash, for production verification.

Result

result string

v0: followed by a base64-encoded zstd-compressed witness blob.

Comparison with Ethereum Standard JSON-RPC

Ethereum Standard

mega_getBlockWitness is not part of the core Ethereum execution JSON-RPC API. It is a MegaETH extension.

MegaETH Node Behavior

MegaETH returns a v0:-prefixed, base64-encoded zstd witness. Requests can select by block hash, or by the paired parent and payload-attributes hashes.

MegaETH Public Gateway

The gateway does not cache witness responses. In an outer batch, if any witness request uses a block number below 7,385,897, at most four mega_getBlockWitness requests are allowed.

Errors

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

Code	Scope	Message	When it happens
-32602	Request	Invalid params	blockNumber missing, invalid hex value, or invalid hash field combination
-32603	Method	Internal error	No witness exists for the requested keys, or the witness service failed
-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 24, 2026

Outcome: success

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "mega_getBlockWitness",
  "params": [
    {
      "blockNumber": "0x7fd",
      "blockHash": "0x262206173864c1e597ab9fcf2f718f95f942907207f4fed97dda66d272c5d4a6"
    }
  ]
}

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": "v0:KLUv/QBgzVUAZJwh\u2026"
}

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/witness.rs
• Code: [email protected]:megaeth-labs/mega-rpc.git @ 06aa35aa95d569c227cc25d2aa12834eb0458aa0: workers/src/services/batch/batch-processor.ts
• Probe: MegaETH Mainnet public endpoint, July 24, 2026