Замена
.badge-default to .badge-dark
.bg-faded to .bg-light
.bg-inverse to .bg-dark
.card-block to .card-body
.card-outline-primary to .border-primary
.card-outline-secondary to .border-secondary
.card-outline-success to .border-success
.card-outline-info to .border-info
.card-outline-warning to .border-warning
.card-primary to .bg-primary
.card-success to .bg-success
.card-info to .bg-info
.card-warning to .bg-warning
.card-danger to .bg-danger
.hidden-xs-down to .d-none .d-sm-block
.hidden-sm-down to .d-none .d-md-block
.hidden-md-down to .d-none .d-lg-block
.hidden-lg-down to .d-none .d-xl-block
.hidden-xs-up to .d-none
.hidden-sm-up to .d-sm-none
.hidden-md-up to .d-md-none
.hidden-lg-up to .d-lg-none
.hidden-xl-up to .d-xl-none
.navbar-toggleable-sm to .navbar-expand-sm
.navbar-toggleable-md to .navbar-expand-md
.navbar-toggleable-lg to .navbar-expand-lg
.navbar-toggleable-xl to .navbar-expand-xl
pull-left and .pull-right to .float-{sm,md,lg,xl}-{left,right,none} или float-left и float-right
<nav class="navbar navbar-expand-md"> to <div class="container-fluid">
.offset-md-4 to .ml-md-auto .mr-md-auto
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