Unusual options activity

Unusual options activity (UOA) is any option trading that a filter flags as abnormal relative to a baseline, usually the contract's volume against its open interest, the premium against what the strike normally trades, or size against a threshold. The label describes the filter, and the answer changes with the baseline.

Senzoukria · Glossary · Updated September 2026

Unusual compared with what

Every UOA alert embeds a comparison. The most common one is Vol/OI: the contract's session volume divided by the open interest published at the prior close. A ratio above one means more contracts traded today than were outstanding yesterday, which points to fresh activity rather than turnover of existing positions. Other baselines are dollar premium against the strike's usual activity, and single-print size against a fixed threshold.

Each baseline has failure modes. Vol/OI becomes unstable when open interest is tiny, and undefined when it is missing; a newly listed strike has no prior open interest at all. Premium baselines depend on how long a history the tool keeps. Size thresholds ignore the multiplier and the underlying's price.

What a flag can and cannot support

  • Supported: this contract saw more activity today than the baseline expected, so it is worth opening the prints.
  • Not supported: who traded, why, whether positions were opened or closed, and which way the underlying will move.
  • Volume above open interest shows turnover; contracts can trade several times in a day, so it does not prove all of them opened new positions.
  • A missing open interest must stay missing. Replacing it with zero produces an infinite ratio and a false alert.

Turning an alert into a question

An alert is useful when it leads to a specific check: open the tape for that contract, look at side classification against synchronised quotes, look for same-time prints on other strikes or expiries that would make it a spread, and note the underlying's price at that moment. Record the alert, the check and what followed, including the cases where nothing followed. A collection of alerts that were only remembered when they worked cannot be tested.

In Senzoukria

The Option Flow module shows a Vol/OI value on every print, computed as the print's size against the contract's standing open interest returned by the configured source; at or above 1 the cell is highlighted, since a single execution as large as the whole open interest cannot be a simple rotation of existing positions. When that open interest is unavailable the table states "Open interest unknown for this contract" rather than inventing a ratio. Premium and Size filters (up to $500K and 250 contracts) narrow the tape, and the SWEEP, GOLDEN and MULTI tags group prints by execution pattern. The site's /flow demonstration uses a different, session-level reading of the same ratio and labels Vol/OI at or above 2 as unusual on generated prints; that is a reading rule to test on real data, not a promise of outcome.

All of this is analysis. The feed runs with the delay of the configured provider, and the options data is billed by that provider.

Common mistakes

  • Reading a Vol/OI of 10 on a strike with a handful of open contracts as meaningful; the denominator is too small.
  • Following an alert on a call without checking for a put leg at the same time.
  • Treating an alert on delayed data as an event happening now.
  • Assuming the underlying tends to move after alerts without having measured it.

This page in other languages

Frequently asked questions

What Vol/OI ratio counts as unusual?
Any threshold is a convention. A ratio above 1 means the session's volume exceeded the previous close's open interest, which is the usual minimum for calling activity fresh; tools often display higher cut-offs to reduce noise. The ratio is only meaningful when the open interest is known and not tiny.
Is unusual options activity a buy signal?
No. It is a filter that selects contracts with abnormal activity relative to a baseline. The direction, the opening or closing nature of the trades and the rest of the trader's position are not in the alert. Whether alerts precede moves in the underlying is an empirical question that has to be measured with a fixed rule and realistic costs.
Why do UOA scanners disagree?
They use different baselines (Vol/OI, premium, size), different histories, different venue coverage and different treatment of missing open interest. The same tape can produce very different alert lists. Read each tool's definition before comparing their output.

Keep reading

Strategy researchTest a trading strategy, from observation to challenge rulesDefine an observation, question it with the copilot, write a rule and explore costs, drawdown and fictional challenge limits in an interactive example.Quant · Start hereQuant trading for beginners: from idea to backtestDefine a testable rule, choose suitable data and evaluate later periods after costs.Order flow · HubOrder flow trading: the complete guideThe hub. What order flow is, what it shows — aggression, delta, imbalance, absorption, liquidity — and the tools that read it, each linked to a full guide.