What is the Shiny default font?

Question

What is the Shiny default font? Where to look it up?

library(shiny)

ui <- fluidPage("What font is used here?")

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

shinyApp(ui, server)

Answer 1

Well using the HTML inspect tool in Internet Explorer we find that Shiny is using "Helvetica Neue",Helvetica,Arial,sans-serif as default text-font and as @Caramiriel already mentioned is this taken from bootstrap.min.css