There are a number of global options that affect Shiny's behavior. These can be set with (for example) options(shiny.trace=TRUE).


A boolean which controls the default behavior when an app is run. See runApp for more information.

A port number that Shiny will listen on. See runApp for more information.

If TRUE, all of the messages sent between the R server and the web browser client will be printed on the console. This is useful for debugging.

If TRUE, enable logging of reactive events, which can be viewed later with the showReactLog function. This incurs a substantial performance penalty and should not be used in production.

This is used to disable graphical rendering by the Cairo package, if it is installed. See plotPNG for more information.

This is a number which specifies the maximum web request size, which serves as a size limit for file uploads. If unset, the maximum request size defaults to 5MB.

Normally, invoking a reactive outside of a reactive context (or isolate()) results in an error. If this is TRUE, don't error in these cases. This should only be used for debugging or demonstrations of reactivity at the console.
The IP address that Shiny should listen on. See runApp for more information.

The number of digits to use when converting numbers to JSON format to send to the client web browser.

This can be a function which is called when an error occurs. For example, options(shiny.error=recover) will result a the debugger prompt when an error occurs.
This can be a function that is called by an observer when an unhandled error occurs in it or an upstream reactive. By default, these errors will result in a warning at the console, and the websocket connection will close.

CSS class names to use for tables.

This controls whether messages for deprecated functions in Shiny will be printed. See shinyDeprecated for more information.