Collaborative Shiny Apps with Automerge • shinysync

Real-time collaborative editing for R and Shiny applications, built on Automerge CRDT.

Installation

pak::pak("shikokuchuo/shinysync")

Features

Component	Description	Sync Server
`editor()`	CodeMirror 6 code editor with cursor-preserving sync	Required
`sync_inputs()`	Synchronize any Shiny inputs across sessions with replay	Not required
`kanban_ui()`	Collaborative kanban board with movable items	Not required
`textarea_ui()`	Basic synchronized textarea	Not required

The editor provides the best experience for collaborative text editing, with proper cursor preservation when remote changes arrive.

sync_inputs makes an entire Shiny app collaborative with a single function call. All scalar inputs (sliders, dropdowns, checkboxes, text inputs) are synchronized automatically. Pair with replay_ui() / replay_server() to step through the full history of input changes.

The kanban module works well without a sync server because its actions (add, toggle, delete, move) are discrete - there’s no cursor position to preserve.

The textarea syncs correctly but has UX limitations (cursor jumps on remote edits), making it suitable only for simple use cases.

Quick Start

Kanban Board (serverless)

library(shiny)
library(shinysync)

ui <- fluidPage(kanban_ui("board"))

server <- function(input, output, session) {
  kanban_server("board", initial_items = list(
    todo = c("Design feature", "Write tests"),
    in_progress = c("Code review"),
    done = c("Deploy v1.0")
  ))
}

shinyApp(ui, server)

Collaborative Shiny App (serverless)

library(shiny)
library(shinysync)

ui <- fluidPage(
  selectInput("dist", "Distribution", c("Normal", "Uniform", "Exponential")),
  sliderInput("n", "Observations", 10, 500, 100),
  plotOutput("plot"),
  replay_ui("timeline")
)

server <- function(input, output, session) {
  replaying <- sync_inputs()
  replay_server("timeline", replaying = replaying)

  output$plot <- renderPlot({
    data <- switch(input$dist,
      Normal = rnorm(input$n),
      Uniform = runif(input$n),
      Exponential = rexp(input$n)
    )
    hist(data, main = input$dist, col = "steelblue", border = "white")
  })
}

shinyApp(ui, server)

Editor (with sync server)

library(shiny)
library(shinysync)
library(autosync)
library(automerge)

sync_server <- amsync_server()
sync_server$start()

doc_id <- create_document(sync_server)
doc <- get_document(sync_server, doc_id)
am_put(doc, AM_ROOT, "text", am_text("Start typing..."))
am_commit(doc, "init")

ui <- fluidPage(editor_output("editor"))

server <- function(input, output, session) {
  output$editor <- editor_render(editor(sync_server$url, doc_id))
}

onStop(function() sync_server$close())
shinyApp(ui, server)

Open either app in multiple browser windows for real-time collaboration.

Vignettes

Collaborative Shiny Apps - Using sync_inputs() with replay
Collaborative Meeting Notes App - Using the CodeMirror editor with a sync server
Collaborative Kanban Board - Serverless task management

Development

To rebuild the bundled JavaScript widget:

cd inst/build
npm install
npm run build

automerge - R bindings for Automerge CRDT
autosync - R sync server for Automerge documents

shinysync