How stop loss orders work in general
A standard stop loss order becomes a market order once the stop price is reached, meaning the fill price can differ from the stop price, sometimes significantly in fast or gapping markets. A stop-limit variant becomes a limit order instead, which controls the fill price but may not execute at all if the market moves through the limit. Understanding this distinction matters because the protection a stop provides is conditional, not guaranteed. Trigger rules, such as whether a stop activates on last trade, bid or ask, vary by broker.
- A stop loss triggers a market order at the stop price; the fill price is not guaranteed.
- A stop-limit order controls fill price but may not execute in a fast-moving market.
- Price gaps, such as overnight moves, can cause fills well below the stop level.
- Trigger conditions and handling outside regular hours differ by broker.


