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The Trades WebSocket streams real-time trade executions for markets. Use this to show live trade feeds, calculate volume, and track market activity. Endpoint: wss://synthesis.trade/ws/trades

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Use cases

Use CaseDescription
Trade feedDisplay a live stream of trades showing price, size, side, and trader info
Volume trackingCalculate real-time trading volume by aggregating trade amounts
Last trade priceShow the most recent execution price as an alternative to mid-market
Whale alertsMonitor for large trades and alert users to significant market activity

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Subscribe

Subscribe using condition IDs (market identifiers). You can subscribe to up to 1,000 markets: 
const ws = new WebSocket("wss://synthesis.trade/ws/trades");

ws.onopen = () => {
    ws.send(JSON.stringify({
        type: "subscribe",
        venue: "polymarket",
        markets: [
            "0xabcdef1234567890abcdef1234567890abcdef12",
            "0x1234567890abcdef1234567890abcdef12345678"
        ]
    }));
};

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Initial response

Upon subscribing, you receive recent historical trades: 
{
    "success": true,
    "response": {
        "trades": [
            {
                "venue": "polymarket",
                "trade": {
                    "tx_hash": "0x9876543210fedcba...",
                    "token_id": "21742633143463906290569050155826241533067272736897614950488156847949938836455",
                    "address": "0x742d35Cc6634C0532925a3b844Bc454e4438f44e",
                    "side": true,
                    "amount": "100",
                    "shares": "153.846",
                    "price": "0.65",
                    "username": "trader123",
                    "image": "https://...",
                    "created_at": "2026-01-01T12:00:00"
                },
                "event": { "..." },
                "market": { "..." }
            }
        ]
    }
}

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Real-time updates

New trades are streamed as they occur: 
{
    "success": true,
    "response": {
        "venue": "polymarket",
        "trade": {
            "tx_hash": "0xfedcba9876543210...",
            "token_id": "21742633143463906290569050155826241533067272736897614950488156847949938836455",
            "address": "0x1234567890abcdef1234567890abcdef12345678",
            "side": false,
            "amount": "500",
            "shares": "714.285",
            "price": "0.70",
            "username": "whale_trader",
            "image": "https://...",
            "created_at": "2026-01-01T12:05:30"
        },
        "market": { "..." }
    }
}

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Complete example: Trade feed

const ws = new WebSocket("wss://synthesis.trade/ws/trades");
const trades = [];
const MAX_TRADES = 50;

ws.onopen = () => {
    ws.send(JSON.stringify({
        type: "subscribe",
        venue: "polymarket",
        markets: ["0xabcdef1234567890abcdef1234567890abcdef12"]
    }));
};

ws.onmessage = (event) => {
    const message = JSON.parse(event.data);
    if (!message.success) return;
    
    const data = message.response;
    
    if (data.trades) {
        trades.push(...data.trades.map(t => t.trade));
        renderTrades();
        return;
    }
    
    trades.unshift(data.trade);
    if (trades.length > MAX_TRADES) {
        trades.pop();
    }
    renderTrades();
};

function renderTrades() {
    const container = document.getElementById("trade-feed");
    container.innerHTML = trades.map(trade => `
        <div class="trade ${trade.side ? 'buy' : 'sell'}">
            <span class="price">${trade.price}</span>
            <span class="size">${trade.shares} shares</span>
            <span class="user">${trade.username || trade.address.slice(0, 8)}</span>
        </div>
    `).join("");
}
Trades include Polymarket profile info (username, image) when available. For anonymous traders, you can display a truncated address instead.