Stocks Block Trades API

Endpoint

Parameters

Request

curl -H "X-Api-Key: YOUR_API_KEY" \
  "https://lab.flashalpha.com/v1/flow/stocks/SPY/blocks?minSize=25000"

import requests

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

const resp = await fetch(
  "https://lab.flashalpha.com/v1/flow/stocks/SPY/blocks",
  { headers: { "X-Api-Key": "YOUR_API_KEY" } }
);
if (!resp.ok) throw new Error(`HTTP ${resp.status}`);
const data = await resp.json();
console.log(data.count + " blocks at minSize " + data.minSize);

{
  "symbol": "SPY",
  "minSize": 25000,
  "count": 0,
  "blocks": [],
  "endpoint_version": "2026.09.30",
  "data_as_of": {
    "node": "fa5",
    "equity_feed": "2026-10-30T13:46:02.995Z",
    "equity_options_feed": "2026-10-30T13:46:02Z",
    "index_feed": "2026-10-30T13:46:02.132Z",
    "index_options_feed": "2026-10-30T13:45:59Z",
    "futures_feed": "2026-10-30T13:45:51.589Z",
    "futures_options_feed": "2026-10-30T13:45:51.596Z",
    "flow_feed": "2026-10-30T13:45:00Z",
    "oi_feed": "2026-10-29T20:00:00Z",
    "macro_feed": "2026-10-29T21:00:20Z"
  }
}

Response Fields

Errors

About

Filters the equity tape to prints at or above minSize shares. Default is 10,000 shares; raise for institutional-only filtering. Each row carries the prevailing bid/ask so you can see how aggressively the print crossed the spread.

Common Use Cases

• Track institutional prints in real time - stream blocks[] to surface every trade at or above the minSize share threshold as it crosses the tape
• Tune the size filter to the name - raise minSize (echoed back as the applied threshold) to isolate genuinely institutional flow on liquid tickers and lower it on thin ones
• Classify the spread aggressor - compare each block's price to its bid/ask to label buyer-initiated (at/above ask) vs seller-initiated (at/below bid) prints
• Read directional bias - tally size by side across the returned blocks to see whether large prints lean accumulation or distribution
• Build a volume-at-price profile - bucket size by price level to map where the big lots transacted for VWAP and support/resistance context
• Flag fresh blocks - watch the newest ts to alert only on prints that just landed rather than replaying the whole buffer

Related

Related reading

• Options flow API: recent trades, blocks & leaderboard - the block-detection workflow applied to the options tape

Complementary endpoints

• Stocks Recent - the full unfiltered tape these blocks are drawn from
• Stocks Summary - headline buy/sell/net totals, including biggestSingleTrade
• Stocks Leaderboard - rank the universe by net notional to find where blocks are clustering
• Options Blocks - the matching block-size prints on the options tape