Every day, option writers in NIFTY, BANKNIFTY and SENSEX put large amounts of money on levels they believe the index won't cross. That money shows up as open interest (OI). Reading where it's concentrated gives you a clear view of the levels the market is defending.

This guide explains how to analyse open interest, how to find support and resistance from OI, and how to use the free OPIFY OI chart to see it at a glance.

What open interest tells you

Open interest is the total number of open option contracts at a strike. Unlike volume, it doesn't reset each day. It builds up as new positions are opened and falls as positions are closed.

In Indian index options, most large OI comes from writers. Writers profit when options expire worthless, so they sell at strikes they expect the index not to reach.

Finding support and resistance from OI

• Highest put OI strike: put writers expect the index to stay above it. Often acts as support.
• Highest call OI strike: call writers expect the index to stay below it. Often acts as resistance.
• The range between them is the zone the market expects for this expiry.

Consistency beats spikes

OI that builds steadily through the day is more reliable than a sudden spike. A spike can be one large trader adjusting a position; steady buildup shows many participants agreeing on a level.

Using the OPIFY OI chart

1. Open the OI chart and select NIFTY, BANKNIFTY or SENSEX.
2. Choose the OI tab to see call and put OI by strike.
3. Use Near ATM to focus on active strikes, or ALL for the full picture.
4. Find the tallest call and put bars: your resistance and support.
5. Check total Call OI and Put OI, shown both in quantity and in value (LTP × quantity).
6. Switch to Change In OI to see which levels are being added to today.

Combine OI with price

OI tells you where levels are. Price tells you whether they are holding.

• Price approaching a high put OI strike and bouncing: support confirmed.
• Price breaking through a high call OI strike with call writers exiting: resistance broken, often with a sharp move as writers cover.

Check price action on the spot chart alongside the OI chart.

Get alerted when sentiment shifts

The OI chart page lets you set an alert when PCR changes, so you know when sentiment flips between bullish and bearish without watching all day.

Common mistakes

• Reading high put OI as bearish.
• Treating OI levels as guaranteed. They can and do break.
• Ignoring which expiry the OI belongs to.
• Relying on OI on expiry day, when positions are closed rapidly.

Frequently asked questions

Is the OI chart free?

Yes, the OI chart is free after login.

Does high OI predict direction?

No. OI shows positioning. It helps you find levels, not predict where the index will go.

This article is for education only and is not investment advice. Options trading involves risk.