How to put scroll bar only for modal-body?

Answer 1

#scroll-wrap {
    max-height: 50vh;
    overflow-y: auto;
}

Using max-height with vh as the unit on the modal-body or a wrapper div inside of the modal-body. This will resize the height of modal-body or the wrapping div(in this example) automatically when a user resize the window.

vh is length unit representing 1% of the viewport size for viewport height.

Browser compatibility chart for vh unit.

Example: https://jsfiddle.net/q3xwr53f/