Insurance Fund
A pool of assets a trading venue or protocol sets aside to absorb losses when a liquidation fails to cover a debt.
On a derivatives venue, positions are liquidated when margin runs low; if the position closes at a worse price than the point where margin was exhausted, the shortfall is drawn from the insurance fund, which is topped up by liquidations that close better than that point. When the fund is depleted, venues fall back on socialized loss mechanisms such as auto-deleveraging, which force-closes some profitable traders' positions to balance the book. Lending protocols use an analogous reserve funded by a share of interest, or a staking module whose stakers can be slashed to cover bad debt. Despite the name, this is not insurance in the regulated sense: there is no policy, no insurer, no claims process, and no obligation to pay, and the fund is simply a buffer that can be exhausted in one volatile session.
In practice
Auto-deleveraging notices on a derivatives venue indicate the insurance fund was insufficient, so profitable counterparties were closed out to cover the shortfall.
The common misunderstanding
That an insurance fund insures users, when it is a venue-owned buffer with no policy or claims process that can be depleted entirely during a single sharp move.