README.md
In bslib: Custom 'Bootstrap' 'Sass' Themes for 'shiny' and 'rmarkdown'

bslib

The bslib R package provides a modern UI toolkit for Shiny and R Markdown based on Bootstrap. It facilitates:

Creation of delightful and customizable Shiny dashboards.
The underlying UI components (e.g., cards, value boxes, sidebars, etc) are also designed to work in other contexts (e.g., in R Markdown).
Custom theming of Shiny apps and R Markdown documents.
Apps can even be themed interactively in real-time.
Use of modern versions of Bootstrap and Bootswatch
Shiny and R Markdown currently default to Bootstrap 3 and may continue to do so to maintain backwards compatibility.

Install the bslib package from CRAN as follows:

install.packages("bslib")

The quickest way to see what {bslib} can do is to run bslib::bs_theme_preview() at the console. This launches a demo app containing both {bslib} and {shiny} UI components as well as an theming widget (bslib::bs_themer()) overlaid on the app. See real-time theming to learn more.

An animation showing bslib theming app. As the user changes the Bootswatch theme and Bootstrap settings, the app's appearance changes in real-time.

Since {bslib} covers a wide array of uses, it has numerous getting started articles, each focusing on a particular interest:

There are two main places to get help with bslib:

The RStudio community is a friendly place to ask any questions (be sure to add a bslib tag when creating a topic).
Stack Overflow is a great source of answers to common bslib questions. It is also a great place to get help, once you have created a reproducible example that illustrates your problem. Use the tags [r][bslib] if you ask a question. Add the tag [bslib] if you are using a Shiny runtime.