modal-dialog-scrollable

.modal-dialog-scrollable {
  display: -ms-flexbox;
  display: flex;
  max-height: calc(100% - 1rem);
}

.modal-dialog-scrollable .modal-content {
  max-height: calc(100vh - 1rem);
  overflow: hidden;
}

.modal-dialog-scrollable .modal-header,
.modal-dialog-scrollable .modal-footer {
  -ms-flex-negative: 0;
  flex-shrink: 0;
}

.modal-dialog-scrollable .modal-body {
  overflow-y: auto;
}

.modal-dialog-centered.modal-dialog-scrollable {
  -ms-flex-direction: column;
  flex-direction: column;
  -ms-flex-pack: center;
  justify-content: center;
  height: 100%;
}

.modal-dialog-centered.modal-dialog-scrollable .modal-content {
  max-height: none;
}

.modal-dialog-centered.modal-dialog-scrollable::before {
  content: none;
}

@media (min-width: 576px) {
  .modal-dialog {
    max-width: 500px;
    margin: 1.75rem auto;
  }
  .modal-dialog-scrollable {
    max-height: calc(100% - 3.5rem);
  }
  .modal-dialog-scrollable .modal-content {
    max-height: calc(100vh - 3.5rem);
  }
  .modal-dialog-centered {
    min-height: calc(100% - 3.5rem);
  }
  .modal-dialog-centered::before {
    height: calc(100vh - 3.5rem);
  }
  .modal-sm {
    max-width: 300px;
  }
}