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
• resizable = TRUE by default — users can drag the edge to resize on desktop

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
• Toolbars -- Compact horizontal strips of buttons, selects, and dividers for card headers and footers

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

1. Choose page layout: page_sidebar() (single-page) or page_navbar() (multi-page)
2. Add theme with bs_theme() (consider Bootswatch for quick start)
3. Create sidebar with inputs for filtering/controls
4. Add value boxes at top for key metrics (set fill = FALSE on container)
5. Arrange cards with layout_column_wrap() or layout_columns()
6. Enable full_screen = TRUE on all visualization cards
7. 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:

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

Guidelines

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

Avoid Common Errors

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

Reference Files

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