The Flexible Box Layout Module in bootstrap is used for designing the flexible and responsive layout structure. It is used in Bootstrap 4.
The d-flex class is used to create a simple flexbox container.
The d-inline-flex class is used to create an inline flexbox container .
Center text:
To center text add .text-center class to the parent element.
Center image:
You can also center the image by adding the .text-center class to the image's parent element.
Center button:
The same as above, add the .text-center to the parent element of the button to center it.
Center column:
By using flexbox you can center the entire the column of the grid.
Flexbox options:
Use justify-content utilities on flexbox containers to change the alignment of flex items on the main axis (the x-axis to start, y-axis if flex-direction: column). Choose from start (browser default), end, center, between, around, or evenly.