Cards

Minor adjustments have been made to the appearance of Bootstrap cards. Borders and and background shades that in .card, .card-header, and .card-footer are turned of by default.

This customization is found in scss/_f-layout-elements.scss in L. Cards. You can revert to Bootstraps default behavior by setting $default-card-borders to or $backgrounds to false.

                                                                    
                                    $default-card-borders: true;
                                    $default-card-backgrounds: true;

                                    @if $default-card-borders == false {

                                        .card,
                                        .card-header,
                                        .card-footer {
                                            border: none;
                                        }

                                    }

                                    @if $default-card-backgrounds == false {
                                        
                                        .card-header,
                                        .card-footer {
                                            background-color: transparent;
                                        }

                                    }
                                
                            

Alternatively, you can add borders back into cards using Bootstrap's border utilities. This method can be particularly advantageous when prototyping because you can create different looks for cards individually.