MessageBar: MessageBar

MessageBarR Documentation



A banner (MessageBar) displays errors, warnings, or important information about an open app or file. For example, if a file failed to upload an error message bar should appear.

For more details and examples visit the official docs. The R package cannot handle each and every case, so for advanced use cases you need to work using the original docs to achieve the desired result.






Props to pass to the component. The allowed props are listed below in the Details section.


  • actions JSX.Element
    The actions you want to show on the other side.

  • ariaLabel string
    A description of the message bar for the benefit of screen readers.

  • className string
    Additional CSS class(es) to apply to the MessageBar.

  • componentRef ⁠IRefObject<IMessageBar>⁠
    Optional callback to access the IMessageBar interface. Use this instead of ref for accessing the public methods and properties of the component.

  • dismissButtonAriaLabel string
    Aria label on dismiss button if onDismiss is defined.

  • dismissIconProps IIconProps
    Custom icon prop to replace the dismiss icon. If unset, default will be the Fabric Clear icon.

  • isMultiline boolean
    Determines if the message bar is multi lined. If false, and the text overflows over buttons or to another line, it is clipped.

  • messageBarIconProps IIconProps
    Custom icon prop to replace the message bar icon. If unset, default will be the icon set by messageBarType.

  • messageBarType MessageBarType
    The type of MessageBar to render.

  • onDismiss ⁠(ev?: React.MouseEvent<HTMLElement | BaseButton | Button>) => any⁠
    Whether the message bar has a dismiss button and its callback. If null, we don't show a dismiss button.

  • overflowButtonAriaLabel string
    Aria label on overflow button if truncated is defined.

  • styles ⁠IStyleFunctionOrObject<IMessageBarStyleProps, IMessageBarStyles>⁠
    Call to provide customized styling that will layer on top of the variant rules.

  • theme ITheme
    Theme (provided through customization.)

  • truncated boolean
    Determines if the message bar text is truncated. If true, a button will render to toggle between a single line view and multiline view. This prop is for single line message bars with no buttons only in a limited space scenario.


Object with shiny.tag class suitable for use in the UI of a Shiny app.

Best practices


  • A message bar is most commonly found near the top of an app, underneath the app's main command bar. For example, the Microsoft Office message bar is positioned beneath the Ribbon, but above the document canvas.

  • Multiple message bars can appear at a time, but a given scenario or related set of scenarios should aim to only show one message bar at a time. Message bars are rarely shown in direct response to an action; rather, they should be shown when there’s something a person should know about the overall app or document.

  • Use the icons options to indicate the message type: the Info icon for information messages; ShieldAlert icon for security-related messages; the Warning icon for non-blocking errors; ErrorBadge icon for critical errors; the Blocked icon for blocking messages; and the Completed icon for success messages.


Message bars should include:


Limit titles to 50 characters (including spaces) to leave room for text expansion when translated. People should be able to scan the title to determine the purpose of the message. Capitalize only the first word of the title and any proper nouns.

Body text

Describe the information or error state concisely, ideally in a single sentence. Limit the message to fewer than 512 characters (including spaces) to leave room for text expansion when translated. Include end punctuation for complete sentences.

Action buttons (Optional)

Offer one to two action buttons to help people solve any errors they're receiving. Limit button text to fewer than 50 charactesr (including spaces) to leave room for translation. Action buttons can have any callback attached to them and should provide people with options to address the notification and dismiss the message bar.

Link (Optional)

Don’t use buttons when a subtler link will suffice. Reserve the use of a button for when the MessageBar has a single ”hero” action that is useful at that particular moment. Avoid using more than one button.

Close button

Always offer a quick way for people to close a message bar, unless there is an issue that must be resolved immediately, such as an expired subscription.



ui <- function(id) {
  ns <- NS(id)

server <- function(id) {
  moduleServer(id, function(input, output, session) {})

if (interactive()) {
  shinyApp(ui("app"), function(input, output) server("app"))

Appsilon/shiny.fluent documentation built on June 4, 2024, 7:02 p.m.