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Documentation Index

Fetch the complete documentation index at: https://docs.backquant.com/llms.txt

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OPEX (options expiration) is the day options contracts expire. In crypto, contracts expire on multiple cadences:
  • Daily expirations — BTC and ETH have daily 0DTE contracts on Deribit
  • Weekly expirations — every Friday, smaller OI
  • Monthly expirations — the last Friday of each month, much larger OI
  • Quarterly expirations — last Friday of March, June, September, December — the heaviest of all
The monthly and quarterly expirations are anchor expiries — institutional positioning concentrates in them, GEX clusters around their strikes, and they often dictate price action in the days leading up to expiry.

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Why this distinction matters

Monthly/quarterly expirations have:
  • 5–10× the OI of weeklies in the same week
  • Roll activity in the 3–5 days before — rolling positions to the next expiry can move spot
  • Pin risk from large dealer hedges unwinding on expiry day
  • Vol regime shifts as the GEX picture redistributes after the expiry-day delta unwind
Weekly expirations matter for short-term gamma but have nowhere near the institutional weight.

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The classification BackQuant returns

Every expiration in our responses comes pre-classified with a type field — you don’t have to parse Deribit-style tokens or detect last-Friday-of-month rules client-side:
TypeDefinitionExample
quarterlyLast Friday of Mar / Jun / Sep / Dec28MAR25, 27JUN25, 26SEP25, 26DEC25
monthlyLast Friday of any other month25APR25 (April 30 is Wednesday → last Friday is the 25th), 30MAY25, 25JUL25
weeklyAny other Friday07MAR25, 14MAR25, 21MAR25, 04APR25, 11APR25
dailyAny non-Friday weekday26MAR25 (Wednesday), 27MAR25 (Thursday)
is_anchor: true is shorthand for monthly or quarterly — the two that institutions watch. Tokens that don’t parse cleanly are returned as unknown and never silently filtered out.

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The /v2/options/opex endpoint

/v2/options/opex bundles everything you need for an OPEX-day workflow into one call: 
curl "https://api.backquant.com/v2/options/opex?symbol=BTCUSDT&horizon=30" \
  -H "X-API-Key: YOUR_API_KEY"
For each upcoming expiration within the horizon, you get:
  • Identification: token, ISO date, DTE, type, is_anchor flag
  • OI block: call_oi, put_oi, total_oi, pcr, notional_oi_usd (= total_oi × spot)
  • IV block: atm_iv, skew_25d, put_25d_iv, call_25d_iv
  • Gamma block: net_gex, call_resistance, put_support (computed per-expiry from the strike × expiry heatmap), max_pain
Plus a next_anchor pointer at the closest monthly/quarterly so you can highlight it in your UI.

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Filtering for the institutional view

Want only the heavyweight expirations? Filter to anchors: 
curl "https://api.backquant.com/v2/options/opex?\
symbol=BTCUSDT\
&horizon=90\
&types=monthly,quarterly" \
  -H "X-API-Key: YOUR_API_KEY"
You’ll get back just the monthlies + quarterlies in the next 90 days, sorted by DTE.

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Same enrichment in /v2/options/expiry-summary

If you already use /v2/options/expiry-summary, each row is enriched with the same type, is_anchor, expiry_date, notional_oi_usd, and max_pain fields. Plus top-level anchor_count and type_counts so you can render summary stats without iterating.

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How to use this in production

Pre-OPEX setup (T-5 to T-1): filter to next anchor, watch the gamma walls move as positions unwind/roll. Big call_resistance moves upward = bullish positioning rolling forward. OPEX day: the max_pain strike on the anchor expiry is a magnet. Combined with GEX levels, you get a tight pin prediction window for the close. Post-OPEX: the next anchor’s expected_move and OI tell you whether positioning has compressed (low IV, low OI = sell-vol environment) or expanded (high IV, high OI = vol expansion likely).

Max pain

The pinning strike on each expiry — a key OPEX-day signal.

What is GEX?

The walls / HVL / support levels OPEX positioning concentrates in.

The IV suite

Term structure flattening / steepening around OPEX is a big signal.