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The eth_sendPrivateTransaction method submits a single signed transaction directly to BlockRazor’s BSC Block Builder without broadcasting it to the public mempool. This protects your transaction from front-running and sandwich attacks by keeping it invisible to other network participants until it is confirmed in a block. Private transactions are routed through BlockRazor’s low-latency validator communication infrastructure, giving them a competitive path to inclusion while maintaining confidentiality.
eth_sendPrivateTransaction is free for all new registered users on BSC with no rate limits. No subscription is required. See Pricing for details on the BSC Package and premium builder features.

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Endpoint

POST https://builder.blockrazor.io/bsc
Authentication is performed via a Bearer token passed in the Authorization header.

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How Private Transactions Work

When you submit a transaction via eth_sendPrivateTransaction, it is held exclusively within BlockRazor’s Block Builder infrastructure. It is never forwarded to the public BSC peer-to-peer network. The transaction remains private until BlockRazor’s Block Builder produces a block that includes it. If the transaction is not included by the maxBlockNumber block, it is silently dropped with no on-chain footprint. This makes private transactions ideal for:
  • MEV-sensitive trades — Prevent sandwich bots from detecting and sandwiching large swaps.
  • Token launches and sniping — Execute at a precise block without exposing intent.
  • Arbitrage — Submit profitable arbitrage without revealing the opportunity to competitors.

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Request

The request follows the standard JSON-RPC 2.0 envelope. The single element of params is a private transaction object.

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Transaction Parameters

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tx
string
required
The signed raw transaction encoded as a hex string prefixed with 0x. This is the same format produced by eth_signTransaction or any standard wallet signing library.
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maxBlockNumber
string
Optional. The maximum block number (as a hex string, e.g., "0xE4E1C5") up to and including which the transaction is eligible for inclusion. If the transaction has not been included by this block, it expires automatically. Omitting this field allows the transaction to remain active for the builder’s default expiry window.

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Code Examples

curl -X POST https://builder.blockrazor.io/bsc \
  -H 'Content-Type: application/json' \
  -H 'Authorization: Bearer YOUR_AUTH_TOKEN' \
  -d '{
    "jsonrpc": "2.0",
    "method": "eth_sendPrivateTransaction",
    "params": [
      {
        "tx": "0xSIGNED_RAW_TRANSACTION_HEX",
        "maxBlockNumber": "0xE4E1C5"
      }
    ],
    "id": 1
  }'

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Response

A successful submission returns the transactionHash of the private transaction. You can use this hash to poll for on-chain confirmation once you expect the transaction to have been included.
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transactionHash
string
The hash of the submitted transaction. Monitor this hash using standard eth_getTransactionReceipt calls against a BSC RPC node to detect when the transaction has been confirmed on-chain.
Response Example
{
  "jsonrpc": "2.0",
  "id": 1,
  "result": "0x4e3f2a1b9c8d..."
}

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Privacy Guarantees

Private transactions are never broadcast to the public mempool. They are only visible on-chain after being included in a block produced by BlockRazor’s Block Builder. If the Block Builder does not produce the target block, the transaction will not appear on-chain for that block—your transaction remains confidential.
Set maxBlockNumber to a value a few blocks beyond your target to give the builder multiple opportunities for inclusion without leaving your transaction active indefinitely. For highly time-sensitive strategies, set a tight maxBlockNumber to ensure the transaction expires cleanly if conditions change.

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