eth_getUncleByBlockHashAndIndex

eth_getUncleByBlockHashAndIndex is the standard Ethereum JSON-RPC call for fetching the uncle (ommer) block header at a given index inside the block identified by hash. On OP Mainnet — the ETH-gas OP Stack rollup at chain ID 10 (0xa) — the method exists for compatibility but always returns null: a single sequencer produces blocks deterministically with no proof-of-work race, so there are no competing siblings and therefore no uncles to reference. The endpoint https://optimism.therpc.io/YOUR_API_KEY accepts the call and responds with null for any block hash and index.

Use cases

• On proof-of-work chains this call lets you compute uncle reward amounts for historical mining analysis — but OP Mainnet has no mining and no uncle rewards, so there is nothing to compute here.
• Uncle rates are sometimes used as a proxy for network latency and mining competition; on OP Mainnet's single-sequencer model that signal does not exist, and the method returns null rather than any rate data.
• If you maintain shared tooling that retrieves uncle header data for cross-chain blockchain research, this endpoint stays available for OP Mainnet for API compatibility but will report no uncle headers.

Parameters

Response

Example request

1curl https://optimism.therpc.io/YOUR_API_KEY \
2  -X POST \
3  -H "Content-Type: application/json" \
4  -d '{
5    "jsonrpc": "2.0",
6    "method": "eth_getUncleByBlockHashAndIndex",
7    "params": [
8        "0x0000000000000000000000000000000000000000000000000000000000000000",
9        "0x0"
10      ],
11    "id": 1
12  }'

Try it live in the Optimism playground.

Errors & troubleshooting

Common pitfalls

• Even on chains that do have uncles, an uncle is only a header — it carries no transactions array, so never parse one out of the result.
• OP Mainnet is not proof-of-work and never had a PoW history; its OP Stack consensus produces no uncles, so every call returns null regardless of the block hash or index you pass.
• On legacy Ethereum PoW a block could reference at most two uncles, so index 0x2 and above always returned null. On OP Mainnet every index — including 0x0 — returns null, so do not treat a null here as a malformed request.

Supported networks

• Mainnet — Chain ID: 10
• Sepolia — Chain ID: 11155420

See also

• eth_getUncleByBlockNumberAndIndex
• eth_getUncleCountByBlockHash
• eth_getBlockByHash

1curl https://optimism.therpc.io/YOUR_API_KEY \
2  -X POST \
3  -H 'Content-Type: application/json' \
4  -d '{"jsonrpc":"2.0","id":1,"method":"eth_getUncleByBlockHashAndIndex","params":["0x0000000000000000000000000000000000000000000000000000000000000000","0x0"]}'