If you take a look at the bootstrap css you will notice the following code:
@media (max-width: 767px) {
.hidden-xs {
display: none !important;
}
}
@media (max-width: 767px) {
.visible-xs {
display: block !important;
}
table.visible-xs {
display: table !important;
}
tr.visible-xs {
display: table-row !important;
}
th.visible-xs,
td.visible-xs {
display: table-cell !important;
}
}
From what you can see there’s not much secret, the classes visible-*
receive display: block
and the hidden-*
receive display: none
, the difference is the use of @media
which verify which resolution specifies to trigger the class.
There is also the class hidden
, acting in all resolutions.
Some examples of how they are executed:Jsfiddle
In the source of version 3 only saw
display:none
being applied. The same for version 4 (developing). If these classes only do this, it just won’t let the browser render/display the content, "underneath the scenes" it will load normally. As I don’t use this framework I don’t know how to answer with details, but apparently does no magic to save resources. :)– Renan Gomes