Shiny Bslib

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 [blocked] 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 [blocked] for detailed guidance.

Cards

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

See cards.md [blocked] for detailed guidance.

Value Boxes

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

See value-boxes.md [blocked] 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 [blocked] 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 [blocked] 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 [blocked] 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 [blocked] 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 [blocked], tooltips-popovers.md [blocked], toasts.md [blocked], and toolbars.md [blocked].

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"
  r

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

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

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