CSS preloaders
In bs4Dash: A 'Bootstrap 4' Version of 'shinydashboard'

library(bslib)
knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)

How to set up a preloader?

Pass the argument preloader to the dashboardPage() function. It expects a list containing all parameters necessary to waiter::waiterShowOnLoad. The duration is automatically handled by listening to the shiny:idle event. Please have a look to the {waiter} documentation for more details.

That's all!

card(
  bs4Dash:::create_link_iframe(bs4Dash:::shinylive_links["inst/examples/vignettes-demos/preloader"]),
  full_screen = TRUE,
  style = "margin: 0 auto; float: none;"
)