eth_getUncleByBlockHashAndIndex

eth_getUncleByBlockHashAndIndex is the standard Ethereum JSON-RPC call that returns the uncle (ommer) block header at a given index inside the block identified by a block hash. It exists for Ethereum-compatibility, and Base — Coinbase's OP Stack optimistic rollup that uses ETH for gas — implements the full eth namespace so tooling works unchanged. The practical reality is that Base has no uncles: blocks are produced by a single sequencer roughly every 2 seconds rather than by competing miners, so no ommer headers are ever recorded. Calls against https://base.therpc.io/YOUR_API_KEY (Base mainnet, chain ID 8453 / 0x2105) therefore return null for every block hash and index.

Use cases

• On proof-of-work chains this method lets you compute uncle reward amounts for historical mining analysis — but on Base there are no mining rewards or uncles, so it has no data to return.
• It is the building block for measuring uncle rates as a proxy for network latency and mining competition; on Base, where a single sequencer orders blocks, that rate is permanently zero.
• Keep it in cross-chain research tooling so the same code path can retrieve uncle header data on PoW networks while gracefully receiving null on Base.

Parameters

Response

Example request

1curl https://base.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 Base 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 expect to read transaction data from the result.
• Base is not a proof-of-work chain; its single-sequencer OP Stack design produces no uncles at all, so queries against any Base block return null rather than a header.
• On legacy PoW history a block can reference at most 2 uncles, meaning index 0x2 and above always return null. On Base every index returns null, so do not write logic that assumes an uncle will eventually appear.

Supported networks

• Mainnet — Chain ID: 8453
• Sepolia — Chain ID: 84532

See also

• eth_getUncleByBlockNumberAndIndex
• eth_getUncleCountByBlockHash
• eth_getBlockByHash

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