you have forgotten width of parent
.parent {_x000D_
display: flex;_x000D_
justify-content: center;_x000D_
position: absolute;_x000D_
width:100%_x000D_
}
_x000D_
<div class="parent">_x000D_
<div class="child">text</div>_x000D_
</div>
_x000D_