startApp: Start Shiny Application (Non-Blocking)

In shiny: Web Application Framework for R

Start Shiny Application (Non-Blocking)

Description

Starts a Shiny application in non-blocking mode, returning a ShinyAppHandle immediately while the app runs in the background. The later event loop services the app, so the R console remains available for interaction.

Usage

startApp(
  appDir = getwd(),
  port = getOption("shiny.port"),
  launch.browser = getOption("shiny.launch.browser", interactive()),
  host = getOption("shiny.host", "127.0.0.1"),
  workerId = "",
  quiet = FALSE,
  display.mode = c("auto", "normal", "showcase"),
  test.mode = getOption("shiny.testmode", FALSE)
)

Arguments

appDir	The application to run. Should be one of the following: A directory containing server.R, plus, either ui.R or a www directory that contains the file index.html. A directory containing app.R. An .R file containing a Shiny application, ending with an expression that produces a Shiny app object. A list with ui and server components. A Shiny app object created by shinyApp().
port	The TCP port that the application should listen on. If the port is not specified, and the shiny.port option is set (with options(shiny.port = XX)), then that port will be used. Otherwise, use a random port between 3000:8000, excluding ports that are blocked by Google Chrome for being considered unsafe: 3659, 4045, 5060, 5061, 6000, 6566, 6665:6669 and 6697. Up to twenty random ports will be tried.
launch.browser	If true, the system's default web browser will be launched automatically after the app is started. Defaults to true in interactive sessions only. The value of this parameter can also be a function to call with the application's URL.
host	The IPv4 address that the application should listen on. Defaults to the shiny.host option, if set, or "127.0.0.1" if not. See Details.
workerId	Can generally be ignored. Exists to help some editions of Shiny Server Pro route requests to the correct process.
quiet	Should Shiny status messages be shown? Defaults to FALSE.
display.mode	The mode in which to display the application. If set to the value "showcase", shows application code and metadata from a DESCRIPTION file in the application directory alongside the application. If set to "normal", displays the application normally. Defaults to "auto", which displays the application in the mode given in its DESCRIPTION file, if any.
test.mode	Should the application be launched in test mode? This is only used for recording or running automated tests. Defaults to the shiny.testmode option, or FALSE if the option is not set.

Details

To stop a non-blocking app from the R console, call handle$stop() on the returned ShinyAppHandle. Despite the similar name, stopApp() is not the counterpart of startApp() — it is for use from inside app code (e.g. server functions, observers, or the onStart hook), where it sets a return value that is later surfaced via handle$result().

Value

A ShinyAppHandle object with methods stop(), status(), url(), and result(). The status() method returns "running", "success", or "error". The result() method throws an error if called while running, or re-throws the error if the app stopped with an error.

Auto-replacement

If another Shiny app is already running in this session when startApp() is called, the running app is stopped before the new one starts. Stopping happens up front, so if the new app then fails to start, no app will be running. You can always call handle$stop() on the existing handle first if you would rather manage the transition yourself.

See Also

runApp() for blocking mode.

Examples

## Not run: 
# Start app in the background
handle <- startApp("myapp")

# Check status
handle$status()
handle$url()

# Stop the app
handle$stop()

## End(Not run)

shiny documentation built on June 21, 2026, 5:07 p.m.