Skill: Electron IPC

Purpose

Use this skill when you need to design or implement communication between Electron's main and renderer processes.

Core Model

• IPC is how Electron processes exchange messages.
• Define your own channel names with ipcMain and ipcRenderer.
• Channels are arbitrary and bidirectional, but keep names explicit and scoped.
• In context-isolated apps, expose narrow preload APIs with contextBridge instead of exposing raw Electron modules to the renderer.

Default Rules

1. Keep privileged work in the main process.
2. Expose small, task-specific preload APIs such as openFile() or setTitle(title).
3. Do not expose ipcRenderer.send, ipcRenderer.invoke, or ipcRenderer.on directly to renderer code.
4. When forwarding events from preload, strip the Electron event object and pass only the data the renderer needs.
5. Prefer namespaced channel names such as dialog:openFile for readability.

Pick the Right Pattern

Need	Renderer API	Main API	Notes
Fire-and-forget renderer -> main	ipcRenderer.send	ipcMain.on	Good for commands with no result
Request/response renderer -> main	ipcRenderer.invoke	ipcMain.handle	Preferred two-way pattern
Push main -> renderer	preload listener wrapper	webContents.send	Main must target a specific window/webContents
Renderer -> renderer	relay through main or MessagePort	main as broker if needed	No direct IPC channel between renderers

Pattern 1: Renderer to Main, One Way

Use this when the renderer triggers a main-process action and does not need a result.

Main

ipcMain.on('set-title', (event, title) => {
  const win = BrowserWindow.fromWebContents(event.sender)
  win?.setTitle(title)
})

Preload

contextBridge.exposeInMainWorld('electronAPI', {
  setTitle: (title) => ipcRenderer.send('set-title', title)
})

Renderer

window.electronAPI.setTitle('New title')

Pattern 2: Renderer to Main, Two Way

Use this when the renderer needs a result from the main process. Prefer this over older reply patterns.

Main

ipcMain.handle('dialog:openFile', async () => {
  const { canceled, filePaths } = await dialog.showOpenDialog()
  return canceled ? undefined : filePaths[0]
})

Preload

contextBridge.exposeInMainWorld('electronAPI', {
  openFile: () => ipcRenderer.invoke('dialog:openFile')
})

Renderer

const filePath = await window.electronAPI.openFile()

Notes

• invoke/handle is the preferred async request-response model.
• Errors from ipcMain.handle are serialized; the renderer does not receive the full original error object.

Pattern 3: Main to Renderer

Use this when the main process needs to push updates into a specific window.

Main

mainWindow.webContents.send('update-counter', 1)

Preload

contextBridge.exposeInMainWorld('electronAPI', {
  onUpdateCounter: (callback) => {
    ipcRenderer.on('update-counter', (_event, value) => callback(value))
  }
})

Renderer

window.electronAPI.onUpdateCounter((value) => {
  // update UI
})

Replying Back

There is no invoke equivalent from main to renderer. If the renderer needs to reply, send a new message back to the main process on a separate channel.

Legacy Patterns

Avoid these unless you have a strong compatibility reason:

• ipcRenderer.send plus event.reply for two-way communication: works, but forces manual reply-channel bookkeeping.
• ipcRenderer.sendSync: blocks the renderer and hurts responsiveness.

Security Checklist

• Never hand the renderer unrestricted Electron or Node access.
• Do not expose raw ipcRenderer methods over contextBridge.
• Wrap listeners so the callback never receives the Electron event object.
• Keep preload APIs minimal and purpose-built.
• Validate inputs in the main process before using privileged APIs.

Serialization Limits

Electron IPC uses the Structured Clone Algorithm.

• Safe: plain objects, arrays, strings, numbers, booleans, and other structured clone compatible values.
• Not safe: DOM objects, Electron objects like BrowserWindow or WebContents, and Node/Electron objects backed by native C++ classes.

Pass serializable data, not live framework objects.

Quick Guidance

• Need a command without a return value: send + on
• Need a result: invoke + handle
• Need to notify a renderer from main: webContents.send
• Need renderer-to-renderer: broker via main or use MessagePort

Reference

• https://www.electronjs.org/docs/latest/tutorial/ipc