Bootstrap 5 (Update 2021)

While the carousel is mostly the same in Bootstrap 5, the concept of left and right have changed to start and end since Bootstrap now has RTL support. Therefore the left/right classes have changed. Here's an example of the multi-item CSS for 4 items (25% width columns)...

@media (min-width: 768px) {
    
    .carousel-inner .carousel-item-end.active,
    .carousel-inner .carousel-item-next {
      transform: translateX(25%);
    }
    
    .carousel-inner .carousel-item-start.active, 
    .carousel-inner .carousel-item-prev {
      transform: translateX(-25%);
    }
}

.carousel-inner .carousel-item-end,
.carousel-inner .carousel-item-start { 
  transform: translateX(0);
}

Since jQuery is no longer required, we use vanilla JS to clone the slides into the carousel-item divs..

let items = document.querySelectorAll('.carousel .carousel-item')

items.forEach((el) => {
    // number of slides per carousel-item
    const minPerSlide = 4
    let next = el.nextElementSibling
    for (var i=1; i<minPerSlide; i++) {
        if (!next) {
            // wrap carousel by using first child
            next = items[0]
        }
        let cloneChild = next.cloneNode(true)
        el.appendChild(cloneChild.children[0])
        next = next.nextElementSibling
    }
})

Bootstrap 5 Multi-item Carousel Demo

Bootstrap 4 (Update 2019)

The carousel has changed in 4.x, and the multi-slide animation transitions can be overridden like this...

.carousel-inner .carousel-item-right.active,
.carousel-inner .carousel-item-next {
  transform: translateX(33.33%);
}

.carousel-inner .carousel-item-left.active, 
.carousel-inner .carousel-item-prev {
  transform: translateX(-33.33%)
}
  
.carousel-inner .carousel-item-right,
.carousel-inner .carousel-item-left{ 
  transform: translateX(0);
}

Bootstrap 4 Alpha.6 Demo
Bootstrap 4.0.0 (show 4, advance 1 at a time)
Bootstrap 4.1.0 (show 3, advance 1 at a time)
Bootstrap 4.1.0 (advance all 4 at once)
Bootstrap 4.3.1 responsive (show multiple, advance 1)new
Bootstrap 4.3.1 carousel with cardsnew

Another option is a responsive carousel that only shows and advances 1 slide on smaller screens, but shows multiple slides are larger screens. Instead of cloning the slides like the previous example, this one adjusts the CSS and use jQuery only to move the extra slides to allow for continuous cycling (wrap around):

Please don't just copy-and-paste this code. First, understand how it works.

Bootstrap 4 Responsive (show 3, 1 slide on mobile)

@media (min-width: 768px) {

    /* show 3 items */
    .carousel-inner .active,
    .carousel-inner .active + .carousel-item,
    .carousel-inner .active + .carousel-item + .carousel-item {
        display: block;
    }
    
    .carousel-inner .carousel-item.active:not(.carousel-item-right):not(.carousel-item-left),
    .carousel-inner .carousel-item.active:not(.carousel-item-right):not(.carousel-item-left) + .carousel-item,
    .carousel-inner .carousel-item.active:not(.carousel-item-right):not(.carousel-item-left) + .carousel-item + .carousel-item {
        transition: none;
    }
    
    .carousel-inner .carousel-item-next,
    .carousel-inner .carousel-item-prev {
      position: relative;
      transform: translate3d(0, 0, 0);
    }
    
    .carousel-inner .active.carousel-item + .carousel-item + .carousel-item + .carousel-item {
        position: absolute;
        top: 0;
        right: -33.3333%;
        z-index: -1;
        display: block;
        visibility: visible;
    }
    
    /* left or forward direction */
    .active.carousel-item-left + .carousel-item-next.carousel-item-left,
    .carousel-item-next.carousel-item-left + .carousel-item,
    .carousel-item-next.carousel-item-left + .carousel-item + .carousel-item,
    .carousel-item-next.carousel-item-left + .carousel-item + .carousel-item + .carousel-item {
        position: relative;
        transform: translate3d(-100%, 0, 0);
        visibility: visible;
    }
    
    /* farthest right hidden item must be abso position for animations */
    .carousel-inner .carousel-item-prev.carousel-item-right {
        position: absolute;
        top: 0;
        left: 0;
        z-index: -1;
        display: block;
        visibility: visible;
    }
    
    /* right or prev direction */
    .active.carousel-item-right + .carousel-item-prev.carousel-item-right,
    .carousel-item-prev.carousel-item-right + .carousel-item,
    .carousel-item-prev.carousel-item-right + .carousel-item + .carousel-item,
    .carousel-item-prev.carousel-item-right + .carousel-item + .carousel-item + .carousel-item {
        position: relative;
        transform: translate3d(100%, 0, 0);
        visibility: visible;
        display: block;
        visibility: visible;
    }

}

<div class="container-fluid">
    <div id="carouselExample" class="carousel slide" data-ride="carousel" data-interval="9000">
        <div class="carousel-inner row w-100 mx-auto" role="listbox">
            <div class="carousel-item col-md-4 active">
                <img class="img-fluid mx-auto d-block" src="//" alt="slide 1">
            </div>
            <div class="carousel-item col-md-4">
                <img class="img-fluid mx-auto d-block" src="//" alt="slide 2">
            </div>
            <div class="carousel-item col-md-4">
                <img class="img-fluid mx-auto d-block" src="//" alt="slide 3">
            </div>
            <div class="carousel-item col-md-4">
                <img class="img-fluid mx-auto d-block" src="//" alt="slide 4">
            </div>
            <div class="carousel-item col-md-4">
                <img class="img-fluid mx-auto d-block" src="//" alt="slide 5">
            </div>
            <div class="carousel-item col-md-4">
                <img class="img-fluid mx-auto d-block" src="//" alt="slide 6">
            </div>
            <div class="carousel-item col-md-4">
                <img class="img-fluid mx-auto d-block" src="//" alt="slide 7">
            </div>
            <div class="carousel-item col-md-4">
                <img class="img-fluid mx-auto d-block" src="//" alt="slide 7">
            </div>
        </div>
        <a class="carousel-control-prev" href="#carouselExample" role="button" data-slide="prev">
            <i class="fa fa-chevron-left fa-lg text-muted"></i>
            <span class="sr-only">Previous</span>
        </a>
        <a class="carousel-control-next text-faded" href="#carouselExample" role="button" data-slide="next">
            <i class="fa fa-chevron-right fa-lg text-muted"></i>
            <span class="sr-only">Next</span>
        </a>
    </div>
</div>

Example - Bootstrap 4 Responsive (show 4, 1 slide on mobile)
Example - Bootstrap 4 Responsive (show 5, 1 slide on mobile)

Bootstrap 3

Here is a 3.x example on Bootply:

You need to put an entire row of images in the item active. Here is another version that doesn't stack the images at smaller screen widths:

EDIT Alternative approach to advance one slide at a time:

Use jQuery to clone the next items..

$('.carousel .item').each(function(){
  var next = $(this).next();
  if (!next.length) {
    next = $(this).siblings(':first');
  }
  next.children(':first-child').clone().appendTo($(this));
  
  if (next.next().length>0) {
    next.next().children(':first-child').clone().appendTo($(this));
  }
  else {
    $(this).siblings(':first').children(':first-child').clone().appendTo($(this));
  }
});

And then CSS to position accordingly...

Before 3.3.1

.carousel-inner .active.left { left: -33%; }
.carousel-inner .next        { left:  33%; }

After 3.3.1

.carousel-inner .item.left.active {
  transform: translateX(-33%);
}
.carousel-inner .item.right.active {
  transform: translateX(33%);
}

.carousel-inner .item.next {
  transform: translateX(33%)
}
.carousel-inner .item.prev {
  transform: translateX(-33%)
}

.carousel-inner .item.right,
.carousel-inner .item.left { 
  transform: translateX(0);
}

This will show 3 at time, but only slide one at a time:

Bootstrap 3.x Demo

Please don't copy-and-paste this code. First, understand how it works. This answer is here to help you learn.

Doubling up this modified bootstrap 4 carousel only functions half correctly (scroll loop stops working)
how to make 2 bootstrap sliders in single page without mixing their css and jquery?
Bootstrap 4 Multi Carousel show 4 images instead of 3

All the above solutions are hacky and buggy. Don't even try. Use other libs. The best I have found - Works great with bootstrap, does not add junk html, highly-configurable, responsive, mobile-friendly etc...

$('.multi-item-carousel').lightSlider({
    item: 4,
    pager: false,
    autoWidth: false,
    slideMargin: 0
});

This is a working twitter bootstrap 3.

Here is the javascript:

$('#myCarousel').carousel({
    interval: 10000
})

$('.carousel .item').each(function(){
    var next = $(this).next();

    if (!next.length) {
        next = $(this).siblings(':first');
    }

    next.children(':first-child').clone().appendTo($(this));

    if (next.next().length>0) {
        next.next().children(':first-child').clone().appendTo($(this));
    }
    else {
        $(this).siblings(':first').children(':first-child').clone().appendTo($(this));
    }
});

And the css:

.carousel-inner .active.left  { left: -33%;             }
.carousel-inner .active.right { left: 33%;              }
.carousel-inner .next         { left: 33%               }
.carousel-inner .prev         { left: -33%              }
.carousel-control.left        { background-image: none; }
.carousel-control.right       { background-image: none; }
.carousel-inner .item         { background: white;      }

You can see it in action at this Jsfiddle

The reason i added this answer because the other ones don't work entirely. I found 2 bugs inside them, one of them was that the left arrow generated a strange effect and the other was about the text getting bold in some situations witch can be resolved by setting the background color so the bottom item wont be visible while the transition effect.

Update 2019-03-06 -- Bootstrap v4.3.1

It seems the new Bootstrap version adds a margin-right: -100% to each item, therefore in the responsive solution given in the most upvoted answer in here, this property should be reset, e.g.:

.carousel-inner .carousel-item {
    margin-right: inherit;
}

A working codepen with v4.3.1 in LESS.

This is what worked for me. Very simple jQuery and CSS to make responsive carousel works independently of carousels on the same page. Highly customizable but basically a div with white-space nowrap containing a bunch of inline-block elements and put the last one at the beginning to move back or the first one to the end to move forward. Thank you insertAfter!

$('.carosel-control-right').click(function() {
  $(this).blur();
  $(this).parent().find('.carosel-item').first().insertAfter($(this).parent().find('.carosel-item').last());
});
$('.carosel-control-left').click(function() {
  $(this).blur();
  $(this).parent().find('.carosel-item').last().insertBefore($(this).parent().find('.carosel-item').first());
});

@media (max-width: 300px) {
  .carosel-item {
    width: 100%;
  }
}
@media (min-width: 300px) {
  .carosel-item {
    width: 50%;
  }
}
@media (min-width: 500px) {
  .carosel-item {
    width: 33.333%;
  }
}
@media (min-width: 768px) {
  .carosel-item {
    width: 25%;
  }
}
.carosel {
  position: relative;
  background-color: #000;
}
.carosel-inner {
  white-space: nowrap;
  overflow: hidden;
  font-size: 0;
}
.carosel-item {
  display: inline-block;
}
.carosel-control {
  position: absolute;
  top: 50%;
  padding: 15px;
  box-shadow: 0 0 10px 0px rgba(0, 0, 0, 0.5);
  transform: translateY(-50%);
  border-radius: 50%;
  color: rgba(0, 0, 0, 0.5);
  font-size: 30px;
  display: inline-block;
}
.carosel-control-left {
  left: 15px;
}
.carosel-control-right {
  right: 15px;
}
.carosel-control:active,
.carosel-control:hover {
  text-decoration: none;
  color: rgba(0, 0, 0, 0.8);
}

<script src=""></script>
<div class="carosel" id="carosel1">
  <a class="carosel-control carosel-control-left glyphicon glyphicon-chevron-left" href="#"></a>
  <div class="carosel-inner">
    <img class="carosel-item" src="" />
    <img class="carosel-item" src="" />
    <img class="carosel-item" src="" />
    <img class="carosel-item" src="" />
    <img class="carosel-item" src="" />
    <img class="carosel-item" src="" />
  </div>
  <a class="carosel-control carosel-control-right glyphicon glyphicon-chevron-right" href="#"></a>
</div>
<div class="carosel" id="carosel2">
  <a class="carosel-control carosel-control-left glyphicon glyphicon-chevron-left" href="#"></a>
  <div class="carosel-inner">
    <img class="carosel-item" src="" />
    <img class="carosel-item" src="" />
    <img class="carosel-item" src="" />
    <img class="carosel-item" src="" />
    <img class="carosel-item" src="" />
    <img class="carosel-item" src="" />
  </div>
  <a class="carosel-control carosel-control-right glyphicon glyphicon-chevron-right" href="#"></a>
</div>

The most popular answer is right but I think the code is uselessly complicated. With the same css, this jquery code is easier to understand I believe:

$('#myCarousel').carousel({
  interval: 10000
})

$('.carousel .item').each(function() {
  var item = $(this);
  item.siblings().each(function(index) {
    if (index < 4) {
      $(this).children(':first-child').clone().appendTo(item);
    }
  });
});

try this.....it work in mine.... code:

<div class="container">
    <br>
    <div id="myCarousel" class="carousel slide" data-ride="carousel">
        <!-- Indicators -->
        <ol class="carousel-indicators">
            <li data-target="#myCarousel" data-slide-to="0" class="active"></li>
            <li data-target="#myCarousel" data-slide-to="1"></li>
            <li data-target="#myCarousel" data-slide-to="2"></li>
            <li data-target="#myCarousel" data-slide-to="3"></li>
        </ol>

        <!-- Wrapper for slides -->
        <div class="carousel-inner" role="listbox">
            <div class="item active">
                <div class="span4" style="padding-left: 18px;">
                    <img src="" class="img-thumbnail">
                    <img src="" class="img-thumbnail">
                    <img src="" class="img-thumbnail">
                </div>
            </div>
            <div class="item">
                 <div class="span4" style="padding-left: 18px;">
                    <img src="" class="img-thumbnail">
                    <img src="" class="img-thumbnail">
                    <img src="" class="img-thumbnail">
                </div>
            </div>
        </div>
        <a class="right carousel-control" href="#myCarousel" role="button" data-slide="next">
            <span class="glyphicon glyphicon-chevron-right" aria-hidden="true"></span>
            <span class="sr-only">Next</span>
        </a>
    </div>
</div>

Natively it is overly complicated and messy to achieve this just with Bootstrap 3.4 Carousel and Bootstrap 4.5 Carousel javascript component features.

OK so you do not want yet another jQuery plugin... I get that.

In my opinion if you're already forced to use jQuery in your project, you might as well have a decent jQuery carousel plugin with lots powerful options.

slick.js - the last carousel you'll ever need - Ken Wheeler

         _ _      _       _
     ___| (_) ___| | __  (_)___
    / __| | |/ __| |/ /  | / __|
    \__ \ | | (__|   < _ | \__ \
    |___/_|_|\___|_|\_(_)/ |___/
                       |__/