How do I know if my extension cord has thermal overload protection?

Look for a small rectangular reset button on the cord head or power strip. If it’s there, the cord has thermal overload protection (a circuit breaker or resettable fuse) that trips when the cord gets too hot or draws too much current—just press the button to reset. If there’s no button, there’s no built-in protection, so don’t run high-draw devices like space heaters or air conditioners on it.