css - Why parent width is fixed and centered, but input width: 100% is outside parent range

Question

As in the title, the details are as shown in the figure. This is the input style.

给我你的怀抱 · Answer

Added box-sizing: border-box;
box-sizing

習慣沉默 · Answer

Placeholder,Placeholder,Placeholder,Placeholder

padding + width is already greater than 100%, the reason is that simple

In the box model width = margin (maybe) + border + padding + width