# Open Interest — StockMojo > Strike-wise OI distribution and intraday buildup analysis - Live page: https://stockmojo.in/open-interest - Content last updated: 2026-04-11 - Platform: StockMojo — free options analytics for Indian markets (NSE F&O) This is a machine-readable markdown mirror of the live tool page. The live page shows real-time NSE data during market hours (09:15-15:30 IST) and supports 200+ F&O symbols via per-symbol URLs like https://stockmojo.in/open-interest/banknifty. ## Frequently asked questions ### What is open interest in options? Open interest (OI) is the total number of outstanding option contracts at a given strike and expiry that have not yet been closed or exercised. Each contract is counted once. Unlike volume, which counts every trade, OI only changes when new positions are opened or existing ones closed. It's a direct measure of where market participants have committed capital. ### How is OI different from volume? Volume counts every trade in a session, including round-trip intraday trades that don't change net positioning. OI counts only outstanding positions at the end of each session (or in real time at NSE). A high-volume, flat-OI session means traders are flipping positions; a high-volume, rising-OI session means new positions are being committed. ### What does an 'OI buildup' tell traders? OI buildup classifies the day's OI change against the day's price change into one of four categories: long buildup (price up + OI up = fresh longs), short buildup (price down + OI up = fresh shorts), long unwinding (price down + OI down = long exits), short covering (price up + OI down = short exits). It's the simplest way to read aggregate intraday positioning. ### What's the difference between long buildup, short buildup, long unwinding, and short covering? Long buildup is fresh bullish positioning. Short buildup is fresh bearish positioning. Long unwinding is bulls exiting (a warning sign for trend continuation). Short covering is bears exiting (often the start of a sharp upmove). The distinction matters because two scenarios with identical price movement can have very different OI signatures and very different follow-through expectations. ### How do you spot a support or resistance level using OI? Strikes with the highest call OI typically act as resistance — they represent the largest concentration of call writers who will defend that level via hedging. Strikes with the highest put OI act as support for the same reason. The StockMojo OI chart highlights these strikes visually so traders can identify the implied price corridor at a glance. ### Why does OI reset at every expiry? OI is a count of contracts that haven't been closed; on expiry day, all contracts in that expiry either exercise (if ITM) or expire worthless (if OTM). Either way, they no longer exist, so OI resets to zero. New OI then accumulates as traders open positions in the next expiry. This is why OI comparisons across expiries require care. ### How often does StockMojo update OI data? Live OI updates on the same cadence as the NSE feed — typically every 1-3 seconds during market hours. The buildup classification recalculates on every refresh so traders always see the current state. Historical OI snapshots are stored for replay via the Timeseries Option Chain tool. ### How should swing traders use OI vs intraday traders? Intraday traders watch live OI buildup for fresh positioning signals — long/short buildups intraday often mark short-term support and resistance. Swing traders care more about cumulative OI distribution across strikes for the upcoming expiry, since that defines the price corridor that institutional writers will defend over multiple sessions. ## How to use the StockMojo Open Interest tool 1. **Select symbol and expiry** — Choose your underlying and the expiry you want to analyze from the selectors at the top. 2. **Read the OI distribution chart** — Identify the strikes with the largest call and put OI bars — these are the implied resistance and support levels for the chosen expiry. 3. **Switch to Change in OI view** — Toggle to the change-in-OI view to see where new positions are being built right now, not just where total positions sit. 4. **Use the buildup classification panel** — Read the long/short buildup and unwinding/covering tags to interpret the day's positioning at a glance. 5. **Confirm with Max Pain and PCR** — Combine the OI picture with the Max Pain target level and the PCR sentiment reading for a complete view before placing a trade. ## Related tools - [Max Pain](https://stockmojo.in/max-pain) — markdown: https://stockmojo.in/max-pain.md - [Put Call Ratio](https://stockmojo.in/put-call-ratio) — markdown: https://stockmojo.in/put-call-ratio.md - [Smart OI](https://stockmojo.in/smart-oi) — markdown: https://stockmojo.in/smart-oi.md ## Glossary Terms used: open-interest, oi-buildup, smart-money, strike-price. Definitions: https://stockmojo.in/glossary