How to center <input> horizontally in a <div>?
This question already has an answer here:
应用以下到容器div 
display: flex;
flex-flow: column wrap;
align-items: center;
div {
  display: flex;
  flex-flow: column wrap;
  align-items: center;
  
}<div style="width: 100vw; position: relative;">
  <h1 style="text-align: center;">Title</h1>
  <input type='text'>
</div>Try this:
 input[type="text"] {
             display: block;
             margin : 0 auto;
        }
Example: Demo
Display block. input elements are inline.
<input type='text' style="display:block; margin : 0 auto;">
