Bootstrap 3 breakpoints and media queries

Question

On the Bootstrap 3 media queries documentation it says:

We use the following media queries in our Less files to create the key breakpoints in our grid

Answer 1

I know this is a bit old, but i thought i would contribute. Basing myself on the answer by @Sophy, this is what I did to add a .xxs breakpoint. I have not taken care of visible-inline, table.visible, etc classes.

/*==========  Mobile First Method  ==========*/

  .col-xxs-12, .col-xxs-11, .col-xxs-10, .col-xxs-9, .col-xxs-8, .col-xxs-7, .col-xxs-6, .col-xxs-5, .col-xxs-4, .col-xxs-3, .col-xxs-2, .col-xxs-1 {
    position: relative;
    min-height: 1px;
    padding-left: 15px;
    padding-right: 15px;
    float: left;
  }

.visible-xxs {
  display:none !important;
}

/* Custom, iPhone Retina */
@media only screen and (min-width : 320px) and (max-width:479px) {

  .visible-xxs {
    display: block !important;
  }
  .visible-xs {
    display:none !important;
  }

  .hidden-xs {
    display:block !important;
  }

  .hidden-xxs {
    display:none !important;
  }

  .col-xxs-12 {
    width: 100%;
  }
  .col-xxs-11 {
    width: 91.66666667%;
  }
  .col-xxs-10 {
    width: 83.33333333%;
  }
  .col-xxs-9 {
    width: 75%;
  }
  .col-xxs-8 {
    width: 66.66666667%;
  }
  .col-xxs-7 {
    width: 58.33333333%;
  }
  .col-xxs-6 {
    width: 50%;
  }
  .col-xxs-5 {
    width: 41.66666667%;
  }
  .col-xxs-4 {
    width: 33.33333333%;
  }
  .col-xxs-3 {
    width: 25%;
  }
  .col-xxs-2 {
    width: 16.66666667%;
  }
  .col-xxs-1 {
    width: 8.33333333%;
  }
  .col-xxs-pull-12 {
    right: 100%;
  }
  .col-xxs-pull-11 {
    right: 91.66666667%;
  }
  .col-xxs-pull-10 {
    right: 83.33333333%;
  }
  .col-xxs-pull-9 {
    right: 75%;
  }
  .col-xxs-pull-8 {
    right: 66.66666667%;
  }
  .col-xxs-pull-7 {
    right: 58.33333333%;
  }
  .col-xxs-pull-6 {
    right: 50%;
  }
  .col-xxs-pull-5 {
    right: 41.66666667%;
  }
  .col-xxs-pull-4 {
    right: 33.33333333%;
  }
  .col-xxs-pull-3 {
    right: 25%;
  }
  .col-xxs-pull-2 {
    right: 16.66666667%;
  }
  .col-xxs-pull-1 {
    right: 8.33333333%;
  }
  .col-xxs-pull-0 {
    right: auto;
  }
  .col-xxs-push-12 {
    left: 100%;
  }
  .col-xxs-push-11 {
    left: 91.66666667%;
  }
  .col-xxs-push-10 {
    left: 83.33333333%;
  }
  .col-xxs-push-9 {
    left: 75%;
  }
  .col-xxs-push-8 {
    left: 66.66666667%;
  }
  .col-xxs-push-7 {
    left: 58.33333333%;
  }
  .col-xxs-push-6 {
    left: 50%;
  }
  .col-xxs-push-5 {
    left: 41.66666667%;
  }
  .col-xxs-push-4 {
    left: 33.33333333%;
  }
  .col-xxs-push-3 {
    left: 25%;
  }
  .col-xxs-push-2 {
    left: 16.66666667%;
  }
  .col-xxs-push-1 {
    left: 8.33333333%;
  }
  .col-xxs-push-0 {
    left: auto;
  }
  .col-xxs-offset-12 {
    margin-left: 100%;
  }
  .col-xxs-offset-11 {
    margin-left: 91.66666667%;
  }
  .col-xxs-offset-10 {
    margin-left: 83.33333333%;
  }
  .col-xxs-offset-9 {
    margin-left: 75%;
  }
  .col-xxs-offset-8 {
    margin-left: 66.66666667%;
  }
  .col-xxs-offset-7 {
    margin-left: 58.33333333%;
  }
  .col-xxs-offset-6 {
    margin-left: 50%;
  }
  .col-xxs-offset-5 {
    margin-left: 41.66666667%;
  }
  .col-xxs-offset-4 {
    margin-left: 33.33333333%;
  }
  .col-xxs-offset-3 {
    margin-left: 25%;
  }
  .col-xxs-offset-2 {
    margin-left: 16.66666667%;
  }
  .col-xxs-offset-1 {
    margin-left: 8.33333333%;
  }
  .col-xxs-offset-0 {
    margin-left: 0%;
  }

}

/* Extra Small Devices, Phones */
@media only screen and (min-width : 480px) {

  .visible-xs {
    display:block !important;
  }

}

/* Small Devices, Tablets */
@media only screen and (min-width : 768px) {

  .visible-xs {
    display:none !important;
  }

}

/* Medium Devices, Desktops */
@media only screen and (min-width : 992px) {

}

/* Large Devices, Wide Screens */
@media only screen and (min-width : 1200px) {

}