How to Send Bitcoin to 200+ Recipients at Once: A Developer’s Guide

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Sending Bitcoin to someone is usually as simple as scanning a QR code or pasting an address — much like using WeChat Pay or Alipay. Enter the amount, confirm with a password, and within minutes to hours, the BTC lands in the recipient’s wallet, no banks involved.

But what if you need to send Bitcoin to hundreds of people at once? Manually repeating this process isn’t just tedious — it's error-prone and inefficient. For developers, especially those managing payouts for mining pools, airdrops, or reward systems, automation becomes essential.

This article dives into how programmers can use Bitcoin RPC (Remote Procedure Call) and coding libraries like BitcoinLib to automate bulk Bitcoin transactions efficiently and securely.

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Why Manual Transfers Don’t Scale

Most standard wallets support sending to multiple recipients — you add several addresses and amounts, then sign one transaction. It works fine for 5 or even 10 people.

But imagine paying out rewards to 200 miners daily. Clicking through a GUI, double-checking every address, avoiding typos — it's unsustainable. Even on desktop, human error increases with repetition.

The solution? Programmatic control via Bitcoin Core’s RPC interface.

Setting Up Bitcoin Core for RPC Access

To interact with Bitcoin programmatically, you need direct access to a running Bitcoin node. Here's how to configure it:

Step 1: Edit bitcoin.conf

Locate your Bitcoin Core data directory and open (or create) the bitcoin.conf file. Add these lines:

server=1
rpcuser=your_username
rpcpassword=your_secure_password

Replace your_username and your_secure_password with strong credentials. This enables the RPC server so your code can communicate with Bitcoin Core.

⚠️ Never expose these credentials publicly. Store them securely.

After saving, restart Bitcoin Core with your data directory specified (e.g., using -datadir=/path/to/data).

Step 2: Choose a Programming Library

Many languages offer Bitcoin RPC libraries. For this guide, we’ll use C# with BitcoinLib, a robust .NET library supporting Bitcoin and other coins like BCH.

You can install it via NuGet Package Manager:

Install-Package BitcoinLib

Or download from GitHub: github.com/GeorgeKimionis/BitcoinLib

Step 3: Set Up Your Development Environment

In Visual Studio, include the necessary namespaces:

using BitcoinLib.ExceptionHandling.Rpc;
using BitcoinLib.Requests.CreateRawTransaction;
using BitcoinLib.Requests.SignRawTransaction;
using BitcoinLib.Responses;
using BitcoinLib.Services.Coins.Base;
using BitcoinLib.Services.Coins.Bitcoin;

Then initialize the service:

ICoinService rpc = new BitcoinService(useTestnet: false);

Set your RPC credentials explicitly in code (or load from config):

rpc.Parameters.RpcUsername = "your_username";
rpc.Parameters.RpcPassword = "your_secure_password";

Step 4: Test the Connection

Before proceeding, verify connectivity:

rpc.Ping();

If no exception is thrown, your app successfully communicates with Bitcoin Core. If not, check:

Once connected, you're ready to build transactions.

Understanding UTXOs: The Building Blocks of Transactions

Bitcoin doesn’t track “account balances” like traditional banking. Instead, it tracks Unspent Transaction Outputs (UTXOs) — chunks of BTC that haven't been spent yet.

To send funds, you must select which UTXOs to spend as inputs.

Fetch all available UTXOs (including zero-confirmation ones):

List<ListUnspentResponse> utxos = rpc.ListUnspent(0);

Each UTXO includes:

Loop through them to inspect:

for (int i = 0; i < utxos.Count; i++)
{
    var uns = utxos[i];
    var tx = rpc.GetTransaction(uns.TxId);
    Console.WriteLine($"Amount: {uns.Amount}, Confirmations: {uns.Confirmations}, Address: {uns.Address}");
}

Constructing a Bulk Transaction

A Bitcoin transaction consists of inputs (which UTXOs to spend) and outputs (where to send funds).

Add Inputs

Select sufficient UTXOs to cover total payout + fees:

var req = new CreateRawTransactionRequest();
req.AddInput(utxos[0].TxId, utxos[0].Vout);
req.AddInput(utxos[1].TxId, utxos[1].Vout);
// Add more as needed

Add Outputs (Bulk Recipients)

Now specify where the money goes:

req.AddOutput("1BPCVbLf7Xz6Y9cKQn7WbuBbDLX6nAhtLr", 0.002m);
req.AddOutput("15H6LPBMEx46U6ryDUnKJoZDAqmmBMpNV6", 0.002m);
req.AddOutput("1DqvWgjp5i9QUzkg1B44crHUkdoRrdrrww", 0.002m);
// ... continue for all recipients

Handle Change (Critical!)

If your total input exceeds outputs + fee, you must return the difference to a change address — otherwise, miners get the rest as a tip!

Example:

decimal totalInputs = utxos[0].Amount + utxos[1].Amount;
decimal totalOutputs = 0.4m; // Sum of all AddOutput amounts
decimal estimatedFee = 0.0005m;
decimal change = totalInputs - totalOutputs - estimatedFee;

if (change > 0)
{
    req.AddOutput("your_change_address_here", change);
}

Failure to do this could cost thousands in lost funds.

Finalize and Broadcast the Transaction

Generate Raw Transaction

string rawTx = rpc.CreateRawTransaction(req);

Decode and inspect it before signing:

var decoded = rpc.DecodeRawTransaction(rawTx);
Console.WriteLine(decoded.ToString());

Verify inputs, outputs, and amounts match expectations.

Sign the Transaction

Unlock your wallet first:

rpc.WalletPassphrase("your_wallet_password", 20); // Unlocked for 20 seconds

Then sign:

var signed = rpc.SignRawTransaction(new SignRawTransactionRequest(rawTx));
string signedHex = signed.Hex;

Broadcast to Network

string txid = rpc.SendRawTransaction(signedHex);
Console.WriteLine("Transaction ID: " + txid);

Check it on blockchain.info or any block explorer using the TXID.

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Frequently Asked Questions (FAQ)

Q: Can I send to 500+ recipients in one transaction?

Yes — technically, there's no hard limit on outputs per transaction. However, larger transactions mean higher fees and potential relay restrictions by some nodes. Always test with small batches first.

Q: How do I reduce transaction fees when sending bulk payments?

Use SegWit addresses (starting with 3 or bc1) and optimize UTXO selection. Avoid dust outputs (<0.0001 BTC), which increase cost without value.

Q: Is it safe to automate wallet operations with code?

Only if done securely. Never hardcode passwords or expose private keys. Run your node locally, use encrypted configs, and limit wallet unlock duration.

Q: What happens if I forget the change output?

The excess BTC becomes a mining fee. For large UTXOs, this could be costly. Always calculate change and include a valid return address.

Q: Can I use testnet for testing bulk transfers?

Absolutely. Set useTestnet: true and use faucets to get tBTC for safe experimentation without financial risk.

Q: Are there alternatives to BitcoinLib?

Yes — popular options include:

Choose based on your stack and security requirements.

Final Thoughts

Automating bulk Bitcoin transfers isn’t just convenient — it’s necessary for scaling blockchain applications like mining pools, airdrops, payroll systems, or decentralized incentives.

By leveraging Bitcoin RPC, UTXO management, and secure coding practices, developers can handle hundreds of transactions reliably and efficiently.

Whether you're building a payout engine or exploring low-level blockchain interactions, mastering raw transactions opens powerful possibilities.

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