eth_getUncleByBlockNumberAndIndex

eth_getUncleByBlockNumberAndIndex is the by-height twin of the hash-based uncle lookup: you give it a block number (or a tag like earliest) and the uncle's index, and it returns that ommer's header. Because you address the block by its position in the chain rather than by a 32-byte hash, this is the variant you reach for when walking a contiguous range of Ethereum history to harvest uncles. The data only exists for the Proof-of-Work era. After The Merge at block 15537393, every slot yields a single PoS block with no ommers, so a query against a recent height resolves to null. Call it on https://ethereum.therpc.io/YOUR_API_KEY (chain ID 1); the payload is the uncle's header, no transactions attached.

Use cases

• Iterate over a numeric range of pre-Merge blocks (everything below 15537393) and collect every uncle header to compute an uncle-rate curve across Ethereum's PoW years.
• Reach early chain history with the earliest tag instead of hardcoding genesis-adjacent heights, which keeps a backfill script readable when crawling the oldest uncles.

Parameters

Response

Example request

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

Try it live in the Ethereum playground.

Errors & troubleshooting

Common pitfalls

• Pointing this at latest or any post-Merge height returns null every time, because PoS Ethereum simply does not produce ommers. Keep your scan bounded below block 15537393 to avoid wasting calls.
• The header you get back has no transactions array. An uncle's transactions never entered the canonical chain, so there is nothing transactional to decode from the result.

Supported networks

• Mainnet — Chain ID: 1
• Sepolia — Chain ID: 11155111

See also

• eth_getUncleByBlockHashAndIndex
• eth_getUncleCountByBlockNumber
• eth_getBlockByNumber

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