eth_getTransactionByBlockHashAndIndex

eth_getTransactionByBlockHashAndIndex returns a single transaction from OP Mainnet by pinning it to a block hash and a zero-based position within that block. It is handy when you have already pulled a block and want the transaction at a known slot without a separate hash lookup. OP Mainnet is an OP Stack optimistic rollup (Bedrock) settling to Ethereum L1, with gas paid in ETH and a block roughly every two seconds, so positions within a block are stable once the block is referenced by hash. Send the request to https://optimism.therpc.io/YOUR_API_KEY (chain ID 10, 0xa).

Use cases

• Enumerate every transaction in a specific OP Mainnet block by stepping the index from 0x0 upward.
• Fetch the first transaction in a block — on OP Mainnet that is the sequencer's L1 attributes deposit — to study transaction ordering and MEV.
• Look up a transaction by its block-position reference when you hold the block hash but not the transaction hash.

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_getTransactionByBlockHashAndIndex",
7    "params": [
8        "0x0000000000000000000000000000000000000000000000000000000000000000",
9        "0x0"
10      ],
11    "id": 1
12  }'

Try it live in the Optimism playground.

Errors & troubleshooting

Common pitfalls

• The index is hex-encoded — pass "0x0" for the first transaction, not the integer 0.
• If the index is at or beyond the block's transaction count, the call returns null rather than an error, so null-check before reading fields.

Supported networks

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

See also

• eth_getTransactionByHash
• eth_getTransactionByBlockNumberAndIndex
• eth_getBlockByHash
• eth_getTransactionReceipt

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_getTransactionByBlockHashAndIndex","params":["0x0000000000000000000000000000000000000000000000000000000000000000","0x0"]}'