eth_getTransactionByBlockNumberAndIndex

eth_getTransactionByBlockNumberAndIndex returns one transaction from OP Mainnet by its zero-based position inside a block addressed by number or by a tag such as latest or pending. It is the number-based companion to the block-hash variant, ideal for sequential scans where you already track heights. 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. Send the request to https://optimism.therpc.io/YOUR_API_KEY (chain ID 10, 0xa).

Use cases

• Iterate block-by-block over the first transaction in each OP Mainnet block — the L1 attributes deposit — for ordering and MEV research.
• Pull a specific transaction from the pending block by its position to inspect what the sequencer has queued next.
• Scan blocks sequentially by height when you have the block numbers and do not need to resolve hashes first.

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_getTransactionByBlockNumberAndIndex",
7    "params": [
8        "latest",
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", not the integer 0, for the first transaction.
• The pending tag's behavior (which transactions appear and in what order) depends on the OP Mainnet sequencer and the node client, so results from pending are not stable between calls.

Supported networks

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

See also

• eth_getTransactionByBlockHashAndIndex
• eth_getTransactionByHash
• eth_getBlockByNumber

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_getTransactionByBlockNumberAndIndex","params":["",""]}'