Send Transaction

A low-latency endpoint to submit signed Solana transactions through 0Block with tip verification and optional preflight/commitment controls.

Overview

• Goal: Land your signed transaction quickly and reliably with Stake-Weighted QoS.

• Tip enforcement: Tx must include a SystemProgram::Transfer or TransferWithSeed of ≥ 0.001 SOL (1,000,000 lamports) to an allowed 0Block tip account.

• Regions: nyc, chi, las, ams, lon, fra, sin, syd.

Prerequisites

1

API Key

Get your API Key

2

Tip

Include a ≥ 0.001 SOL transfer to one of the official tip accounts.

3

Signed Tx

Provide a fully signed transaction (base64 or base58).

Endpoint & Headers

Endpoint format

POST https://{region}.0block.io/?api_key=<YOUR_API_KEY>

Example

https://nyc.0block.io/?api_key=<YOUR_API_KEY>

Headers

Content-Type: application/json

Request Schema (JSON-RPC 2.0)

0Block accepts standard JSON-RPC with method: "sendTransaction":

{
  "jsonrpc": "2.0",
  "id": "optional-correlation-id",
  "method": "sendTransaction",
  "params": [
    "<SIGNED_TRANSACTION>",               // required: base64 or base58 string
    {
      "encoding": "base64",               // optional: "base64" | "base58"
      "skipPreflight": false,             // optional: boolean
      "preflightCommitment": "processed", // optional: "processed" | "confirmed" | "finalized"
      "maxRetries": 3,                    // optional: integer
      "minContextSlot": 265470000         // optional: integer
    }
  ]
}

Parameters

Path	Type	Required	Description
jsonrpc	string	No	Use "2.0" (standard marker).
id	string | number	No	Echoed back in responses for correlation.
method	string	Yes	Must be "sendTransaction".
params[0]	string	Yes	Signed Solana transaction as base64 or base58. Base64 padding optional.
params[1].encoding	enum	No	"base64" or "base58". If omitted, auto-detected (tries base64, then base58).
params[1].skipPreflight	boolean	No	true to bypass simulation for lower latency.
params[1].preflightCommitment	enum	No	"processed" | "confirmed" | "finalized" for preflight checks.
params[1].maxRetries	integer	No	Max automatic retry attempts upstream.
params[1].minContextSlot	integer	No	Minimum slot context required by the client.

Tip requirement (enforced): If the transaction does not include a qualifying System transfer ≥ 1,000,000 lamports to an allowed tip account, it will be rejected.

Examples

Minimal (auto-detect encoding)

{
  "jsonrpc": "2.0",
  "id": 1,
  "method": "sendTransaction",
  "params": ["BASE64_OR_BASE58_SIGNED_TX"]
}

With options

{
  "jsonrpc": "2.0",
  "id": "tx-42",
  "method": "sendTransaction",
  "params": [
    "BASE64_SIGNED_TX",
    {
      "encoding": "base64",
      "skipPreflight": false,
      "preflightCommitment": "confirmed",
      "maxRetries": 5,
      "minContextSlot": 265470000
    }
  ]
}

cURL

curl -X POST 'https://nyc.0block.io/?api_key=<YOUR_API_KEY>' -H "Content-Type: application/json"   -d '{
        "jsonrpc": "2.0",
        "id": "tx-42",
        "method": "sendTransaction",
        "params": [
          "BASE64_SIGNED_TX",
          { "encoding": "base64", "preflightCommitment": "confirmed", "maxRetries": 5 }
        ]
      }'

JavaScript (Node)

import fetch from "node-fetch";

async function sendTx(apiKey, txBase64) {
  const body = {
    jsonrpc: "2.0",
    id: "tx-42",
    method: "sendTransaction",
    params: [txBase64, { encoding: "base64", preflightCommitment: "confirmed" }]
  };

  const res = await fetch("https://nyc.0block.io/?api_key=<YOUR_API_KEY>", {
    method: "POST",
    headers: {
      Authorization: `Bearer ${apiKey}`,
      "Content-Type": "application/json"
    },
    body: JSON.stringify(body)
  });

  return res.json();
}

Responses

0Block relays the upstream Solana JSON-RPC response on success, typically:

{
  "jsonrpc": "2.0",
  "result": "5t4eBfVv8A3tN6d2zjZphqStjc6b4YbTL7Yt8Y6XWf9",
  "id": "tx-42"
}

Where result is the transaction signature.

On failure, you’ll receive a JSON-RPC error object (either from 0Block pre-checks or from upstream).

0Block Error Codes (Pre-validation)

code	message	When it happens
-32700	Parse error	Malformed JSON.
-32600	Invalid Request: missing method	method missing/empty.
-32601	Method not found	Not "sendTransaction".
-32602	Invalid params: ...	params not array, missing params[0], or decode failure.
-32000	Invalid transaction: ...	Bad framing (sigs/message OOB).
-32000	Invalid transaction message: ...	Message parse failure (legacy or v0).
-32603	Server misconfiguration: no tip pubkeys loaded	Server not configured with tip allowlist.
-32001	Tip verification failed[: reason]	No qualifying tip or below min lamports.
-32002	v0 address table resolution required	Tip destination only resolvable via lookup (not in static keys).
-32098	Upstream error	Solana RPC unavailable / 5xx.

Tip Accounts (Allowlist)

7ryAvKtymdDdnSqE6g8ctS7sMcmxDCZbzXoRDWSLzero
6646q6HMnzAE7BUhsWma86SebPm2VC9bW9tsDJsDzero
2ZH2unJ7NaCu3kiXaiJPDwjSjDNudFgqhMetSDJGzero
9yXPwviBkVAEWGEbCVkYhzyN7fsrybfDSYv7SeTXzero
4LFeE3G7eJDHoStjPrga6MyJdbrMG924MAyLTp3Rzero
GHjaNw8Sd8ArWZt2UqoH2rGYtzt2MspUmxcAshFkzero
MbCZkyVkpADL3kqWPf94bWXNgzwNeyjUqUXBZn5zero
AYXWDKX1wWwS6Rcydx2Z6QjS1SZhW69z2pxoEpuRzero
8kR3r5aaenaauC1qFcBVwAtMAP9GAANthrsLToe3zero
24wwbjb4vXDpfGHhH61JsPkRQzSnCFWUeiuQpXkZzero

Best Practices

• Choose the nearest region to minimize latency.

• Use skipPreflight: true only for high-confidence transactions.

• Adjust preflightCommitment for consistency vs speed.

• Add retries (maxRetries) for transient upstream errors.

• Ensure tip destination appears in static accounts for v0 messages.

• Reuse connections (HTTP/2 keep-alive) for high throughput.

Regions

Region	Endpoint
🇺🇸 North America (East)	https://nyc.0block.io
🇺🇸 North America (Central)	https://chi.0block.io
🇺🇸 North America (West)	https://las.0block.io
🇳🇱 Netherlands	https://ams.0block.io
🇬🇧 United Kingdom	https://lon.0block.io
🇩🇪 Germany	https://fra.0block.io
🇸🇬 Singapore	https://sin.0block.io
🇦🇺 Australia	https://syd.0block.io