eth_getTransactionByBlockNumberAndIndex

eth_getTransactionByBlockNumberAndIndex returns one transaction identified by two coordinates: the block (given as a hex-encoded block number or one of the tags latest, earliest, pending, safe, finalized) and the transaction's zero-based index within that block. Both parameters are passed as 0x-prefixed hex strings.

Reach for it when you already know a transaction's slot in a block — for example while iterating a Polygon block transaction-by-transaction, or when you have an index from a prior eth_getBlockByNumber call and want only that one body rather than the whole block. This is the by-number counterpart of eth_getTransactionByBlockHashAndIndex; use that sibling when you hold the block hash instead, or eth_getTransactionByHash when you already have the transaction's own hash.

Polygon runs Bor consensus with a ~2.1 s block time, so a typical block carries roughly 50–150 transactions. If the block does not exist, or the index is out of range for that block, result is null rather than an error — check for null before reading fields.

Positional params array: [blockNumber, transactionIndex].

Response fields

The transaction object carries the standard EVM fields:

Errors arrive in the standard JSON-RPC error object; the extra fields move into error.data.

A missing block or an out-of-range index is not an error — it returns result: null. See the shared Errors reference for the full envelope, the HTTP-status mapping, and error.data field definitions.

JavaScript (fetch)

const res = await fetch("https://api.triport.io/polygon", {
  method: "POST",
  headers: {
    "Authorization": `Bearer ${process.env.TRIPORT_API_KEY}`,
    "Content-Type": "application/json",
  },
  body: JSON.stringify({
    jsonrpc: "2.0",
    id: 1,
    method: "eth_getTransactionByBlockNumberAndIndex",
    params: ["latest", "0x0"],
  }),
});


const { result, error } = await res.json();
if (error) throw new Error(`${error.code}: ${error.message}`);
console.log(result === null ? "no such transaction" : result.hash);

TypeScript SDK (@triport/sdk)

import { Triport } from "@triport/sdk";


const client = new Triport({ token: process.env.TRIPORT_API_KEY! });


type Transaction = { hash: string; from: string; to: string | null; value: string };


const tx = await client.polygon.rpc<Transaction | null>(
  "eth_getTransactionByBlockNumberAndIndex",
  ["0x3b9aca00", "0x0"],
);
console.log(tx?.hash ?? "no such transaction");

Python (triport-sdk)

import os
from triport import Triport


client = Triport(token=os.environ["TRIPORT_API_KEY"])


tx = client.polygon.rpc(
    "eth_getTransactionByBlockNumberAndIndex",
    ["latest", "0x0"],
)
print(tx["hash"] if tx else "no such transaction")

• Zero-based index. 0x0 is the first transaction in the block. Use eth_getBlockTransactionCountByNumber to learn the valid index range first.
• Null on miss. An out-of-range index or a non-existent block returns result: null, not an error — guard for null before reading fields.
• Hex numerics. value, gas, gasPrice, nonce, … are hex strings; convert with base 16 before doing arithmetic. Values are in wei.
• Polygon chain ID. chainId is 0x89 (137) for Polygon mainnet.
• No daily cap. Rate limiting is sustained-rps-per-tier with a 2× burst allowance — there is no daily quota. See Rate limits.
• Related: eth_getTransactionByBlockHashAndIndex (same lookup, by block hash) · eth_getTransactionByHash (by transaction hash) · eth_getBlockByNumber (the whole block at once).