I've noticed that many traders don't pay enough attention to a useful tool like open interest. And yet, it is one of the most reliable indicators for understanding what is really happening in the derivatives market.

Open interest shows the total number of active, open contracts for a specific asset. When two traders enter into a futures contract, open interest increases by one. When one of them closes a position, it decreases. Simple but powerful. This is not the same as trading volume. Volume counts every trade, while the open interest indicator tracks only the number of open positions.

What's interesting: when both indicators—volume and open interest—rise simultaneously, it usually signals a truly strong trend. New players are entering the market, positions are growing, and momentum is strengthening. But if you see volume increasing while open interest is falling, that's a different story. It means traders are closing their positions. This could be a sign of a potential reversal or trend weakening.

In practice, I often use open interest together with other tools—volatility, price action, moving averages. For example, if you see rising open interest against high volume and moving averages give a bullish signal, that's a pretty strong argument for buying. The Relative Strength Index (RSI) further confirms such a picture.

It's important to understand that this indicator mainly works in futures and options markets, as well as in crypto derivatives. Its application on spot stock markets is limited. Professional traders rely on open interest to assess market sentiment and confirm their trading decisions.

One feature to note: open interest data is usually updated at the end of the trading day, not in real-time like volume. This should be considered when analyzing.

When open interest increases during an uptrend, it usually means new participants are continuing to open buy positions—a classic bullish scenario. Conversely, if open interest declines while volume is rising in a sideways market, it may indicate traders are closing positions in anticipation of a clear direction.

Of course, like any indicator, open interest is not a panacea. It can lag and should be used in conjunction with other analysis tools. But if you're serious about trading derivatives, understanding this metric provides a real competitive edge. It reveals the true market sentiment and helps avoid false signals. Ultimately, open interest is one of the keys to making more informed trading decisions and increasing your chances of success in a dynamic market.