BNB Up/Down order book microstructure on Polymarket

• 645 BNB Up/Down markets, led by 438 five-minute contracts
• Average market spread of 0.0415 (median 0.0300) - the third widest of the eight assets
• Average top-of-book liquidity of about $11,710 per market over three days
• 1.30% of the last 24 hours of BNB book snapshots were crossed
• All 645 markets settle on chainlink_twap reference prices

At 2026-10-17 the archive holds 645 BNB Up/Down markets: 438 at 5 minutes, 194 at 15 minutes and 13 at 4 hours. The series is roughly the same shape as Solana and XRP but a little shorter, reflecting BNB's smaller share of crypto market activity.

255 markets have resolved, and they lean noticeably down: 105 up to 150 down, only 41.2% up. That is the most down-biased resolution balance in the basket - BTC by contrast resolved 52.3% up. Over a single measurement window a spread this large can be noise, but it is worth flagging for any directional strategy run on BNB.

BNB averages a 0.0415 spread with a median of 0.0300 - three ticks wide at the median, roughly four times the touch you see on Bitcoin. It sits in the second tier with Dogecoin (0.0363): traded, but not cheap to enter and exit.

Depth reinforces the picture. Three-day average top-of-book liquidity is about $11,710 per BNB market, comparable to Dogecoin's $12,054 and well under Solana's $18,132. A size that would not register on BTC can visibly walk a BNB book, so transaction-cost assumptions matter more here.

import requests

BASE = "https://api.polyorderbooks.com/v1"
HEADERS = {"X-API-Key": "your-key"}

slug = "bnb-updown-5m-1787486400"
r = requests.get(
    f"{BASE}/markets/{slug}/metrics",
    headers=HEADERS,
    params={"start_ts": 1787486400, "end_ts": 1787486700, "resolution": "1s"},
)
r.raise_for_status()
pts = r.json()["data"]
print("points:", len(pts), "first spread:", pts[0]["spread"])

BNB's crossed-book rate is 1.30% over the last 24 hours (6,746 of 518,421 snapshots) - less than half of Solana's 2.63%. A wider, thinner book that needs less frequent repricing produces fewer momentary crosses, so BNB behaves more like Dogecoin than like the majors.

Even so, the filter still applies: about one in 77 BNB snapshots is internally inconsistent, and those are exactly the snapshots where a naive fill model would print a free profit that never existed.

All 645 BNB Up/Down markets settle on a Chainlink TWAP reference price. Reference coverage for BNB began at 11:52 UTC on the measurement day, capturing 34,173 observations by 2026-10-17 - a shorter series than the BTC/Ethereum cohort that starts at 07:38 because the feed was extended to BNB later that morning.

That timing matters if you are validating settlement for older BNB markets: the archive's reference series for the asset is younger than the market series, so the earliest BNB books predate the reference capture. Match your grading checks to the reference window you actually have.

The Starter plan is free, includes order books, prices, and metrics at 250ms resolution, with 3 days of history, 60 requests/min, 1,000/day, 1 free AI backtest, and 3 strategy backtests. No credit card required.

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• Polymarket BNB data
• Crypto microstructure data
• Order book API guide