eth_getUncleByBlockNumberAndIndex

eth_getUncleByBlockNumberAndIndex returns the header of an uncle (ommer) block at a given index inside the block at a specified height or block tag. It is the height-based twin of eth_getUncleByBlockHashAndIndex and exists on Polygon — the MATIC-fueled PoS chain at https://polygon.therpc.io/YOUR_API_KEY (chain ID 137, 0x89) — purely for Ethereum JSON-RPC compatibility. Polygon's Bor/Heimdall Proof-of-Stake consensus with L1 checkpoints does not create uncle blocks, so on this network the call returns null at every height. It stays in the interface so standard Ethereum tooling keeps working unmodified.

Use cases

• On Proof-of-Work networks you would scan a range of block numbers to collect every uncle header for uncle-rate analysis; on Polygon PoS each height yields null, so this loop reports no uncles by design.
• Block tags such as "earliest" let you reach genesis-era data without first resolving a hash — handy in generic tooling, though on Polygon the result here is still null and you would read the canonical block with eth_getBlockByNumber instead.

Parameters

Response

Example request

1curl https://polygon.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 Polygon playground.

Errors & troubleshooting

Common pitfalls

• Polygon PoS produces no uncles, so this method returns null for recent blocks — and in fact for every height. A null here is the expected result on Polygon, not a sign of a missing block or a bad request.
• Even where uncles exist, an uncle response is a header only and contains no transactions array, so never try to read transactions from it.

Supported networks

• Mainnet — Chain ID: 137
• Amoy — Chain ID: 80002

See also

• eth_getUncleByBlockHashAndIndex
• eth_getUncleCountByBlockNumber
• eth_getBlockByNumber

1curl https://polygon.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"]}'