Implementation:Puppeteer Puppeteer Dialog

Sources	packages/puppeteer-core/src/api/Dialog.ts
Domains	Browser Dialogs, User Interaction, Event Handling
Last Updated	2026-02-12

Overview

Dialog is the abstract base class that represents browser dialog boxes (alert, confirm, prompt, beforeunload) dispatched by a Page via the dialog event.

Description

The Dialog class models native browser dialogs that are triggered by JavaScript calls such as alert(), confirm(), prompt(), or by the beforeunload event. Dialog instances are dispatched by the Page class through the dialog event.

Each dialog instance stores three private properties: the dialog type (from Protocol.Page.DialogType), the message text displayed in the dialog, and a default value (relevant only for prompt dialogs, empty string otherwise). These are exposed through the type(), message(), and defaultValue() accessor methods.

The class provides two user-action methods: accept() resolves the dialog affirmatively (optionally providing text input for prompt dialogs), and dismiss() rejects the dialog. Both methods include an assertion guard via the handled flag to prevent double-handling -- attempting to accept or dismiss an already-handled dialog throws an error.

The actual protocol communication for handling the dialog is delegated to the abstract handle() method, which concrete subclasses must implement.

Usage

Dialog instances are received through the page.on('dialog', ...) event listener. They must be either accepted or dismissed exactly once. If no dialog handler is registered, the browser will auto-dismiss dialogs.

Code Reference

Source Location

packages/puppeteer-core/src/api/Dialog.ts

Signature

export abstract class Dialog {
  constructor(type: Protocol.Page.DialogType, message: string, defaultValue?: string);
  type(): Protocol.Page.DialogType;
  message(): string;
  defaultValue(): string;
  async accept(promptText?: string): Promise<void>;
  async dismiss(): Promise<void>;
  protected abstract handle(options: { accept: boolean; text?: string }): Promise<void>;
}

Import

import type {Dialog} from 'puppeteer-core/src/api/Dialog.js';

I/O Contract

Inputs

Parameter	Type	Description
type (constructor)	Protocol.Page.DialogType	The dialog type: 'alert', 'confirm', 'prompt', or 'beforeunload'
message (constructor)	string	The message displayed in the dialog
defaultValue (constructor)	string	Default value for prompt dialogs (defaults to empty string)
promptText (accept)	undefined	Optional text to enter in a prompt dialog before accepting

Outputs

Method	Return Type	Description
type()	Protocol.Page.DialogType	The type of the dialog
message()	string	The message displayed in the dialog
defaultValue()	string	The default prompt value, or empty string
accept()	Promise<void>	Resolves when the dialog has been accepted
dismiss()	Promise<void>	Resolves when the dialog has been dismissed

Usage Examples

import puppeteer from 'puppeteer';

const browser = await puppeteer.launch();
const page = await browser.newPage();
page.on('dialog', async dialog => {
  console.log(dialog.message());
  await dialog.dismiss();
  await browser.close();
});
await page.evaluate(() => alert('1'));

// Handle a confirm dialog
page.on('dialog', async dialog => {
  if (dialog.type() === 'confirm') {
    await dialog.accept();
  }
});
const result = await page.evaluate(() => confirm('Proceed?'));
console.log(result); // true

// Handle a prompt dialog with input text
page.on('dialog', async dialog => {
  if (dialog.type() === 'prompt') {
    console.log('Default value:', dialog.defaultValue());
    await dialog.accept('My input text');
  }
});
const name = await page.evaluate(() => prompt('Enter your name:', 'Anonymous'));
console.log(name); // 'My input text'

Related Pages

• Environment:Puppeteer_Puppeteer_Node_18_Runtime