Open Interest (OI)
A futures contract can't exist on its own. For someone to open a long (a bet on up), someone else must open a short (a bet on down) on the other side. Open interest is the sum of all such contracts — one long matched with one short — that haven't been closed yet. That's why, across the whole market, longs and shorts are always exactly equal in size.
In numbers: if trader A opens a new 1 BTC long and trader B opens a new 1 BTC short and they match, OI increases by 1 BTC. Later, when A closes the position and the counterparty is also someone closing theirs, OI decreases by 1 BTC. But if existing holders merely pass positions between each other, trades happened yet OI stays flat.
It's easy to confuse with volume, so here's a handy distinction: volume is the water that has flowed past; OI is the water currently pooled. However big volume gets, if it was all hand-changing with no new entries, OI doesn't grow.
Traders often read price and OI as a pair. Price rising with rising OI reads as 'new buying money pushing it up'; price rising while OI falls reads as 'shorts bailing out (short covering).' The downside gets two readings too, giving four combinations that folk wisdom uses to guess what's going on under the hood.
But that combination-reading is just folk wisdom. OI tells you how much is at stake, not which way those positions will resolve. History has cases where OI spiked and price surged — and cases where it crashed hard.
What the data actually shows
OI itself isn't among the 28 chart signals Barobara verifies. Its closest relatives are the volume-family signals that measure market activity — for example, the historical record of volume spike + green candle (1h) shows that even these activity signals barely moved the odds of what came next away from a coin flip. 'The market is hot' and 'the market is going somewhere' are different pieces of information — that's the picture the data paints. You can check other signals' results yourself in the setup statistics.Common misconceptions
"Rising OI is a bullish signal" makes the rounds constantly, but OI carries no direction information. Longs and shorts are always 1:1 in futures, so rising OI doesn't mean 'more people betting on up' — it means 'both sides put more chips on the table.' Another misconception is "OI and volume are basically the same thing." Volume can hit record highs on pure hand-changing while OI stays flat, and there are quiet days when OI just builds.
FAQ
Q. Does price go up when OI rises?
No. Rising OI means new positions were added equally on the long and short side, so it's separate from direction. The safer reading: with more chips on the table, when one side eventually breaks, cascading liquidations can make the move bigger.
Q. What does it mean when OI suddenly plunges?
It means a lot of positions were closed at once. The classic case is a sharp crash or spike force-liquidating leveraged positions and sending OI tumbling. But the OI drop by itself can't tell you which way price goes afterward.