What a stop-out is
A stop-out is the broker automatically closing your positions — starting with the biggest loser — because your margin level fell to the stop-out threshold. It happens after the margin call warning if losses keep growing. The purpose is to prevent your losses from exceeding what your account can cover.
How the level works
Brokers set a margin-call level and a lower stop-out level (for example, a call at 100% and stop-out at 50% of margin level — the exact numbers vary). When equity falls to the stop-out percentage of used margin, positions are closed one by one until the level is restored.
Why it hits
Over-leverage is the root cause: positions too large for the account, so a modest adverse move drives the margin level down fast. No stop-losses, correlated trades losing together, or a sharp market move can all accelerate it.
How to avoid it
Trade small relative to your balance, so a normal move barely dents your margin level. Always use stop-losses to cap each trade before margin ever becomes the issue. Keep plenty of free margin, avoid stacking correlated positions, and know your broker's call and stop-out levels in advance.
Broker's fault or yours?
A stop-out is a protective mechanism operating as designed, and it is driven by your sizing — so it is on your side. Being stopped out is a strong signal that leverage was too high, and the fix is smaller positions, not blaming the broker.