Many people open the door a few inches with the latch on, thinking it’s safe enough. But if someone pushes hard from outside, that latch may not hold.
Using the peephole first lets you see who’s there without opening anything. If they still seem suspicious but you need to talk, a door chain gives you some barrier while speaking. It’s not perfect protection, but it’s extra time and distance between you and a stranger.
Combining both—first see, then partially open with a chain if truly needed—is safer than automatically cracking the door open every time the bell rings.
