eth_getTransactionByBlockNumberAndIndex

eth_getTransactionByBlockNumberAndIndex returns one transaction from a Base block, located by the block's number (or a tag like latest, safe, or finalized) and the transaction's zero-based index within it. It is the number-based sibling of eth_getTransactionByBlockHashAndIndex, handy when you scan the chain by height rather than by hash. Base is Coinbase's OP Stack optimistic rollup that settles to Ethereum L1 and meters gas in ETH, with the sequencer sealing a block about every 2 seconds. Send the call to https://base.therpc.io/YOUR_API_KEY (chain ID 8453, hex 0x2105) with a block tag and a hex index; you get the transaction object, or null if the block or index is out of range.

Use cases

• Sweep Base block-by-block by height, pulling the first transaction (0x0) of each block to study sequencer ordering and MEV patterns.
• Peek at a transaction's position in the next block using the pending tag, where node support allows it.
• Scan sequentially when you already track block numbers and have no need to resolve a block hash first — one fewer round trip per block.

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

Try it live in the Base playground.

Errors & troubleshooting

Common pitfalls

• The index is hex-encoded: pass "0x0" for the first transaction, never the integer 0.
• The pending tag is not uniform — transaction ordering and even availability under it differ between node clients, so do not build hard guarantees on the pending view of a Base block.

Supported networks

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

See also

• eth_getTransactionByBlockHashAndIndex
• eth_getTransactionByHash
• eth_getBlockByNumber

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