To help manage risk and maintain orderly markets, we apply Open Interest (OI) limits on a per-market basis.
Open Interest (OI) is the total number of active perpetual contracts currently open across all traders in a market.
Why do OI limits exist?
OI limits help ensure the exchange can support trading activity during volatile conditions by limiting how much new exposure can be added to a single market.
What happens when an OI limit is reached?
OI limits are designed to prevent new exposure from increasing further, while still allowing traders to reduce or close positions.
Here’s what to expect:
You can still place orders and they can rest on the order book.
OI limits are checked when an order would fill (when orders match).
Trades are still allowed if the fill would reduce open interest (for example, closing a position).
A fill is blocked only when:
the trade would increase open interest, and
executing the fill would push the market above its OI limit
If a fill is blocked, your order will fail with an error such as “order breaches OI cap”, and the resting order on the book remains.
How OI limits are measured
Each market has two types of OI limits:
OI size limit - The maximum number of contracts that can be open in that market.
OI notional limit - The maximum USD value of open interest that can be open in that market.
This is calculated using the market’s Mark Price.
Both limits apply at the same time. The effective limit is whichever one is reached first.
Common scenarios
Two traders are opening new positions (may be blocked)
If a trade would increase OI and the market is already at (or near) its limit, the fill may be rejected.
One trader is closing (allowed)
If at least one side of the trade is closing or reducing an existing position, the fill is allowed even if the market is at its limit.
Both traders are closing (allowed)
Trades that reduce open interest are allowed.
Market notional changes due to price movement
OI notional is measured in USD using the Mark Price, so the notional value of a market’s open interest can change as price moves. In these situations, the limit is enforced by blocking trades that would add more open interest, rather than forcing existing traders to close positions.
Liquidations (allowed)
Liquidations must be able to execute. Closing orders created as part of a liquidation process are allowed to match even if the market is at or above its limit.