How to Build a Solana Copy Trading Bot That Actually Works

#solana #crypto #javascript #tutorial

Copy trading on Solana is one of the most requested features in crypto trading bots. Here's how I implemented it in @solscanitbot and the architectural decisions behind it.

The Problem

You want to automatically mirror another wallet's trades. When they buy a token, you buy it. When they sell, you sell. Simple concept, surprisingly tricky to implement.

Two Approaches

1. WebSocket Monitoring (Complex)

Subscribe to account changes via Helius WebSocket
Parse transaction logs in real-time
High complexity, many edge cases

2. Snapshot-Diff (Simple, What I Use)

Take snapshot of target wallet's token holdings
Wait 60 seconds
Take new snapshot
Diff the two: new tokens = buys, missing tokens = sells

I chose snapshot-diff. Here's why:

Why Snapshot-Diff Wins

Simpler code — ~50 lines vs 200+ for WebSocket
More reliable — WebSocket connections drop; polling always works
Easier to debug — you can log each snapshot
60-second latency is fine — for copy trading, seconds don't matter

Implementation

async function checkCopyTrades() {
  for (const [chatId, targets] of Object.entries(copyTargets)) {
    for (const target of targets) {
      const currentHoldings = await getWalletTokens(target.wallet);
      const prevHoldings = target.lastSnapshot || {};

      // Find new tokens (buys)
      for (const [mint, amount] of Object.entries(currentHoldings)) {
        if (!prevHoldings[mint]) {
          await executeCopyBuy(chatId, mint, target.buyAmount);
        }
      }

      // Find removed tokens (sells)
      for (const [mint, amount] of Object.entries(prevHoldings)) {
        if (!currentHoldings[mint]) {
          await executeCopySell(chatId, mint);
        }
      }

      target.lastSnapshot = currentHoldings;
    }
  }
}

Edge Cases

Partial sells: If they reduce position but don't fully exit, compare amounts
Multiple targets: Users can copy multiple wallets simultaneously
Position sizing: Don't copy the whale's 100 SOL buy with your 0.5 SOL
Failed trades: Retry once, then notify the user

Getting Wallet Token Holdings

Use getTokenAccountsByOwner RPC call:

const accounts = await fetch(RPC_URL, {
  method: 'POST',
  body: JSON.stringify({
    jsonrpc: '2.0', id: 1,
    method: 'getTokenAccountsByOwner',
    params: [walletAddress, { programId: TOKEN_PROGRAM_ID }, { encoding: 'jsonParsed' }]
  })
});

Live in Action

Try it free: /copy <wallet_address> in @solscanitbot

Or get the full source code with all 42 commands for 2 SOL.

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