The International Residential Code (IRC) requires an emergency escape and/or rescue opening in every basement and sleeping room. There has to be a way for (a) people to safely leave the room and (b) first responders to enter during a fire or other emergency.²
Dimension requirements determine these opening sizes, so they have to be pretty big. Sometimes they’re doors, but they can also be windows. They’re often called “egress windows.”
Because the purpose of an egress window is to escape, we don’t recommend using locks or window well covers. Those devices keep intruders out, but they also make it much harder to exit during an emergency! Similarly, keep your egress windows clear of furniture and other debris so you can quickly get out.
We recommend going with security lights, cameras, window film, or entry sensors on egresses.