What is an Open Interest API?

An Open Interest (OI) API is a data endpoint that gives you the total open interest for a derivatives market — the number of open futures or options contracts that haven't been settled or closed yet, typically expressed in both contract count and notional USD value.

What open interest actually means: OI counts outstanding positions, not trading volume. Every time a trader opens a new position, OI goes up by one contract; every time a position is closed, it goes down. So OI is a gauge of how much money is currently committed to a market — not how much is moving through it. Rising OI alongside rising price usually suggests new money entering (trend confirmation), while falling OI means positions are being closed out.

What these APIs typically return:

• Open interest value — total notional USD committed
• OI by contract count — per coin (e.g. BTC), per exchange, per timeframe
• OI change % — 24h/1h/4h movement
• OI split — long vs. short, or per expiry date
• Often bundled with funding rate and long/short ratios, since those three together describe positioning in a perp market

Why traders use it: it's the core signal for derivative-positioning analysis — spotting liquidation cascades, gauging leverage in the market, and confirming whether a price move has real conviction behind it (new positions) or is just short covering (closing positions).

A real-world note: in this app, when I pull up a coin that trades on Binance Futures, the funding rate and open interest in the report come from exactly this kind of data source (per Binance Futures). If you have a specific coin in mind, I can pull its current OI/funding figures — just tell me which one.