Options Block Trades API

Endpoint

curl -H "X-Api-Key: YOUR_API_KEY" \
  "https://lab.flashalpha.com/v1/flow/options/SPY/blocks?minSize=250"

import requests

resp = requests.get(
    "https://lab.flashalpha.com/v1/flow/options/SPY/blocks",
    headers={"X-Api-Key": "YOUR_API_KEY"}
)
data = resp.json()
print(f"{data['count']} blocks at minSize {data['minSize']}")

const resp = await fetch(
  "https://lab.flashalpha.com/v1/flow/options/SPY/blocks",
  { headers: { "X-Api-Key": "YOUR_API_KEY" } }
);
const data = await resp.json();
console.log(data.count + " blocks at minSize " + data.minSize);

Response

{
  "symbol": "SPY",
  "minSize": 250,
  "count": 2,
  "blocks": [
    {
      "ts": "2026-05-12T18:41:55.108Z",
      "expiry": "2026-05-15",
      "strike": 600.0,
      "right": "C",
      "price": 1.85,
      "size": 1500,
      "side": "buy"
    },
    {
      "ts": "2026-05-12T18:38:12.402Z",
      "expiry": "2026-06-20",
      "strike": 590.0,
      "right": "P",
      "price": 4.30,
      "size": 800,
      "side": "sell"
    }
  ]
}

Key Response Fields

Errors

About

Filters the option tape to only prints at or above minSize contracts. Default is 100 contracts but you can raise it for institutional-only filtering. Returns rows in the same shape as the recent feed minus instrument id, bid, and ask.

Common Use Cases

• Track institutional-only flow - raise minSize to 500+ and watch blocks[] to surface only large single-ticket prints worth reacting to
• Detect multi-leg sweeps - cluster blocks[] by ts across strikes and expiries to identify a single sweep routed across venues
• Read directional intent - combine side with right (e.g. buy calls vs buy puts) to tell bullish bets from hedges or bearish positioning
• Score conviction by notional - multiply size by price on each block to rank prints by dollars committed, not just contract count
• Spot event positioning - scan large prints on specific expiry legs into earnings or macro catalysts
• Build a day sentiment overlay - tally buy-side versus sell-side size across blocks to gauge net institutional pressure

Related

Related reading

• Options sweep detection: the 500ms rule - how block prints coalesce into cross-venue sweeps
• Flow Signals API: scoring unusual options activity - turn large prints into a ranked unusual-activity score

Complementary endpoints

• Options Recent - the full tape these blocks are filtered from, with bid/ask context
• Options Summary - aggregate buy/sell volume the blocks contribute to
• Options Leaderboard - rank the contracts these blocks land on
• Flow Signals - scored unusual-activity layer built on this flow