Scrolling content with more length than the viewport :
When the content in the modal is more than the user’s viewport, the modals become scrollable, and they scroll independent to that of the page. The source code remains the same as above.
Vertically centered Modal :
To vertically center a modal, you should add a ‘modal-dialog-centered’ class to the div that has ‘modal-dialog’ class.
Modals of different sizes :
You can use different sizes for your modals. Add one of the following classes to the div having ‘modal-dialog’ class. Below is a table describing the different sizes provided by Bootstrap. You can also use custom sizes using JS or CSS.