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Pro plan required. Pending trade events are available on Pro and Enterprise plans.
Pending events are detected from the Polygon mempool before the transaction is mined. They arrive on average ~3 seconds before the corresponding confirmed event, typically 3–5 seconds early. This gives you an early signal for copytrading, alerting, or analytics — before the trade is finalized on-chain.

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How It Works

  1. A trade transaction enters the Polygon mempool
  2. Predexon detects it and emits a pending event
  3. ~3–5 seconds later, the transaction is mined and a confirmed event is emitted
  4. Match the two events by tx_hash — the confirmed event supersedes the pending one

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Enabling Pending Events

Add a status filter to your orders subscription. There are three modes:
status ValueWhat You ReceivePlan Required
"confirmed" (default)Only confirmed (mined) eventsAny plan
"all"Both pending + confirmed eventsPro+
"pending"Only pending (mempool) eventsPro+
Omitting status defaults to "confirmed" — fully backward compatible.

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Subscribe to both pending and confirmed

{
  "action": "subscribe",
  "platform": "polymarket",
  "version": 1,
  "type": "orders",
  "filters": {
    "users": ["*"],
    "status": "all"
  }
}

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Subscribe to pending only

{
  "action": "subscribe",
  "platform": "polymarket",
  "version": 1,
  "type": "orders",
  "filters": {
    "users": ["*"],
    "status": "pending"
  }
}

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Update an existing subscription

{
  "action": "update",
  "subscription_id": "sub_abc123",
  "filters": {
    "users": ["*"],
    "status": "all"
  }
}
Dev tier clients requesting status: "all" or status: "pending" will receive a PLAN_REQUIRED error.

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What Differs Between Pending and Confirmed

Every order_filled event includes a status field ("pending" or "confirmed"). Most fields are identical, but a few differ:
FieldPendingConfirmedWhy
status"pending""confirmed"
priceMay differ slightlyExactCan differ by a fraction of a cent if partial fills change the effective price
shares / shares_normalizedMay differ slightlyExactIf the tx partially fills, final on-chain amounts may differ
feeEstimatedExactActual fee may vary slightly after on-chain settlement
log_indexnullIntegerNo log exists yet for pending
order_hashnullStringNot available for pending events
timestampTime seen in mempoolBlock timestamp
tx_hashExactExactSame hash — use this to match pending → confirmed
All other fields — user, taker, token_id, side, and all metadata (market slug, title, outcome, etc.) — are identical between pending and confirmed.

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Accuracy

~98% of pending events have price, shares, and fee values identical to the final confirmed event. The remaining ~2% may differ slightly due to partial fills or settlement adjustments — typically by a fraction of a cent on price or a few wei on fee.

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Important Caveats

  • Not guaranteed to confirm — some pending transactions may be dropped, reverted, or replaced. Treat status: "pending" as a strong signal, not a guarantee.
  • Only order_filled events — pending detection applies to trade fills only. Fee refunds, activity, and lifecycle events remain confirmed-only.
  • Match by tx_hash — when the confirmed event arrives, it supersedes the pending one. Use tx_hash to correlate them.

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Example: Handling Both Pending and Confirmed

const pendingTrades = new Map(); // tx_hash → pending data

ws.onmessage = (event) => {
  const msg = JSON.parse(event.data);

  if (msg.type === 'event' && msg.data.event_type === 'order_filled') {
    const data = msg.data;

    if (data.status === 'pending') {
      // Early signal from mempool — act on it, but expect confirmation
      pendingTrades.set(data.tx_hash, data);
      console.log(`[PENDING] ${data.side} ${data.outcome} ${data.shares_normalized} @ ${data.price}`);
      console.log(`  Market: ${data.title}`);
      console.log(`  Maker: ${data.user}`);
    }

    if (data.status === 'confirmed') {
      const wasPending = pendingTrades.delete(data.tx_hash);
      const label = wasPending ? '[CONFIRMED]' : '[NEW]';
      const value = data.shares_normalized * data.price;
      console.log(`${label} ${data.side} ${data.outcome} ${data.shares_normalized} @ ${data.price}`);
      console.log(`  Market: ${data.title}`);
      console.log(`  Value: $${value.toFixed(2)}`);
    }
  }
};