Modern Shiny Apps with bslib

Build professional Shiny dashboards using bslib's Bootstrap 5 components and layouts. This skill focuses on modern UI/UX patterns that replace legacy Shiny approaches.

Quick Start

Single-page dashboard:

library(shiny)
library(bslib)

ui <- page_sidebar(
  title = "My Dashboard",
  theme = bs_theme(version = 5),  # "shiny" preset by default
  sidebar = sidebar(
    selectInput("variable", "Variable", choices = names(mtcars))
  ),
  layout_column_wrap(
    width = 1/3,
    fill = FALSE,
    value_box(title = "Users", value = "1,234", theme = "primary"),
    value_box(title = "Revenue", value = "$56K", theme = "success"),
    value_box(title = "Growth", value = "+18%", theme = "info")
  ),
  card(
    full_screen = TRUE,
    card_header("Plot"),
    plotOutput("plot")
  )
)

server <- function(input, output, session) {
  output$plot <- renderPlot({
    hist(mtcars[[input$variable]], main = input$variable)
  })
}

shinyApp(ui, server)

Multi-page dashboard:

ui <- page_navbar(
  title = "Analytics Platform",
  theme = bs_theme(version = 5),
  nav_panel("Overview", overview_ui),
  nav_panel("Analysis", analysis_ui),
  nav_panel("Reports", reports_ui)
)

Core Concepts

Page Layouts

page_sidebar() -- Single-page dashboard with sidebar (most common)
page_navbar() -- Multi-page app with top navigation bar
page_fillable() -- Viewport-filling layout for custom arrangements
page_fluid() -- Scrolling layout for long-form content

See page-layouts.md for detailed guidance.

Grid Systems

layout_column_wrap() -- Uniform grid with auto-wrapping (recommended for most cases)
layout_columns() -- 12-column Bootstrap grid with precise control

See grid-layouts.md for detailed guidance.

Cards

Primary container for dashboard content. Support headers, footers, multiple body sections, and full-screen expansion.

See cards.md for detailed guidance.

Value Boxes

Display key metrics and KPIs with optional icons, sparklines, and built-in theming.

See value-boxes.md for detailed guidance.

Navigation

Page-level: page_navbar() for multi-page apps
Component-level: navset_card_underline(), navset_tab(), navset_pill() for tabbed content

See navigation.md for detailed guidance.

Sidebars

Page-level: page_sidebar() or page_navbar(sidebar = ...)
Component-level: layout_sidebar() within cards
Supports conditional content, dynamic open/close, accordions

See sidebars.md for detailed guidance.

Filling Layouts

The fill system controls how components resize to fill available space. Key concepts: fillable containers, fill items, fill carriers. Fill activates when containers have defined heights.

See filling.md for detailed guidance.

Theming

bs_theme() with Bootswatch themes for quick styling
Custom colors: bg, fg, primary affect hundreds of CSS rules
Fonts: font_google() for typography
Dynamic theming: input_dark_mode() + session$setCurrentTheme()

See theming.md for detailed guidance.

UI Components

Accordions -- Collapsible sections, especially useful in sidebars
Tooltips -- Hover-triggered help text
Popovers -- Click-triggered containers for secondary UI/inputs
Toasts -- Temporary notification messages

See accordions.md, tooltips-popovers.md, and toasts.md.

Icons

Recommended: bsicons package (Bootstrap Icons, designed for bslib):

bsicons::bs_icon("graph-up")
bsicons::bs_icon("people", size = "2em")

Browse icons: https://icons.getbootstrap.com/

Alternative: fontawesome package:

fontawesome::fa("envelope")

Accessibility for icon-only triggers: When an icon is used as the sole trigger for a tooltip, popover, or similar interactive element (no accompanying text), it must be accessible to screen readers. By default, icon packages mark icons as decorative (aria-hidden="true"), which hides them from assistive technology.

bsicons::bs_icon(): Provide title — this automatically sets a11y = "sem"

tooltip(
  bs_icon("info-circle", title = "More information"),
  "Tooltip content here"
)

fontawesome::fa(): Set a11y = "sem" and provide title

tooltip(
  fa("circle-info", a11y = "sem", title = "More information"),
  "Tooltip content here"
)

The title should describe the purpose of the trigger (e.g., "More information", "Settings"), not the icon itself (e.g., not "info circle icon").

Special Inputs

input_switch() -- Toggle switch (modern checkbox alternative)
input_dark_mode() -- Dark mode toggle
input_task_button() -- Button for long-running operations
input_code_editor() -- Code editor with syntax highlighting
input_submit_textarea() -- Textarea with explicit submission

See inputs.md for detailed guidance.

Common Workflows

Building a Dashboard

Choose page layout: page_sidebar() (single-page) or page_navbar() (multi-page)
Add theme with bs_theme() (consider Bootswatch for quick start)
Create sidebar with inputs for filtering/controls
Add value boxes at top for key metrics (set fill = FALSE on container)
Arrange cards with layout_column_wrap() or layout_columns()
Enable full_screen = TRUE on all visualization cards
Add thematic::thematic_shiny() for plot theming

Modernizing an Existing App

See migration.md for a complete mapping of legacy patterns to modern equivalents. Key steps:

Replace fluidPage() with page_sidebar() or page_navbar()
Replace fluidRow()/column() with layout_columns()
Wrap outputs in card(full_screen = TRUE)
Add theme = bs_theme(version = 5)
Convert key metrics to value_box() components
Replace tabsetPanel() with navset_card_underline()

Guidelines

Prefer bslib page functions (page_sidebar(), page_navbar(), page_fillable(), page_fluid()) over legacy equivalents (fluidPage(), navbarPage())
Use layout_column_wrap() or layout_columns() for grid layouts instead of fluidRow()/column(), which don't support filling layouts
Wrap outputs in card(full_screen = TRUE) when building dashboards -- full-screen expansion is a high-value feature
Set fill = FALSE on layout_column_wrap() containers holding value boxes (they shouldn't stretch to fill height)
Pin Bootstrap version: include theme = bs_theme(version = 5) or a preset theme
Use thematic::thematic_shiny() in the server so base R and ggplot2 plots match the app theme
Use responsive widths like width = "250px" in layout_column_wrap() for auto-adjusting columns
Group sidebar inputs with accordion() when sidebars have many controls
See migration.md for mapping legacy Shiny patterns to modern bslib equivalents

Avoid Common Errors

Avoid directly nesting card() containers. navset_card_*() functions are already cards; nav_panel() content goes directly inside them without wrapping in card()
Only use layout_columns() and layout_column_wrap() for laying out multiple elements. Single children should be passed directly to their container functions.
Never nest page_*() functions. Only use one top-level page function per app.

Reference Files

migration.md -- Legacy Shiny to modern bslib migration guide
page-layouts.md -- Page-level layout functions and patterns
grid-layouts.md -- Multi-column grid systems
cards.md -- Card components and features
value-boxes.md -- Value boxes for metrics and KPIs
navigation.md -- Navigation containers and patterns
sidebars.md -- Sidebar layouts and organization
filling.md -- Fillable containers and fill items
theming.md -- Basic theming (colors, fonts, Bootswatch). See shiny-bslib-theming skill for advanced theming
accordions.md -- Collapsible sections and sidebar organization
tooltips-popovers.md -- Hover tooltips and click-triggered popovers
toasts.md -- Temporary notification messages
inputs.md -- Special bslib input widgets
best-practices.md -- bslib-specific patterns and common gotchas

shiny-bslib