Implementation:Getgauge Taiko Install Chromium

Knowledge Sources	Taiko
Domains	Browser_Automation, Testing
Last Updated	2026-02-12 00:00 GMT

Overview

Concrete tool for the post-install Chromium download system provided by the Taiko library.

Description

The Install Chromium module is responsible for automatically downloading the correct Chromium browser binary as a post-install step during npm install taiko. It acts as the entry point that orchestrates the browser acquisition process, delegating the actual download and extraction work to the BrowserFetcher class.

The main() function in lib/install.js performs a series of guard checks before initiating the download. It first inspects the TAIKO_SKIP_CHROMIUM_DOWNLOAD environment variable and the npm config equivalent (NPM_CONFIG_TAIKO_SKIP_CHROMIUM_DOWNLOAD) to determine if the user has explicitly opted out of the download. It then checks whether the target revision is already present locally, avoiding redundant downloads. Only when all checks pass does it invoke BrowserFetcher.download().

The BrowserFetcher class (defined in lib/browser/fetcher.js) handles the low-level mechanics of downloading and extracting the Chromium archive. It constructs a platform-specific download URL via BrowserMetadata, downloads the zip archive over HTTP/HTTPS with optional proxy support, extracts it using extract-zip, sets executable permissions, and cleans up the temporary zip file. After a successful download, the install script removes any previously downloaded Chromium revisions to conserve disk space.

A progress bar is displayed during download using the progress npm package, providing real-time feedback on download progress including file size, percentage, and estimated time remaining.

Usage

This module is invoked automatically during npm install taiko as a post-install script defined in package.json. It is not intended to be called directly by users. However, its behavior can be controlled through environment variables:

Set TAIKO_SKIP_CHROMIUM_DOWNLOAD=true to skip the download entirely (useful in CI environments where Chromium is pre-installed).
Set TAIKO_BROWSER_PATH to point to a custom browser binary, making the bundled download unnecessary.
Set proxy environment variables (HTTP_PROXY, HTTPS_PROXY) for downloading behind corporate firewalls.

Code Reference

Source Location

Repository: Taiko
File (entry point): lib/install.js
Lines: L81-111 (main function), L33-43 (onSuccess), L48-54 (onError), L56-74 (onProgress)
File (fetcher): lib/browser/fetcher.js
Lines: L45-131 (BrowserFetcher class), L141-181 (downloadFile), L188-192 (extractZip), L194-219 (httpRequest)

Signature

// lib/install.js - Entry point
function main() -> void

// lib/browser/fetcher.js - BrowserFetcher class
class BrowserFetcher {
  constructor(options?: { path?: string, platform?: string })
  async download(revision: string, progressCallback?: (downloadedBytes: number, totalBytes: number) => void) -> Promise<RevisionInfo>
  async remove(revision: string) -> Promise<void>
  canDownload() -> Promise<boolean>
  localRevisions() -> Promise<string[]>
}

Import

// Called automatically as npm post-install script
// Not intended for direct import

// Internal usage within the codebase:
const BrowserFetcher = require('./browser/fetcher');
const BrowserMetadata = require('./browser/metadata');
const browser = require('../package.json').taiko.browser;

I/O Contract

Inputs

Name	Type	Required	Description
TAIKO_SKIP_CHROMIUM_DOWNLOAD	env var (string)	No	Set to any truthy value (except "false") to skip the Chromium download entirely
NPM_CONFIG_TAIKO_SKIP_CHROMIUM_DOWNLOAD	env var (string)	No	npm config alternative to skip the Chromium download
TAIKO_BROWSER_PATH	env var (string)	No	Path to a custom browser binary; when set, the bundled download is unnecessary
revision	string (from package.json)	Yes (internal)	Chromium revision number read from `package.json` taiko.browser field
progressCallback	function(number, number)	No	Callback invoked with (downloadedBytes, totalBytes) during download

Outputs

Name	Type	Description
Chromium binary	File on disk	Extracted Chromium binary placed in `node_modules/taiko/.local-chromium/{platform}-{revision}/`
Console output	string	Status messages printed to stdout indicating download progress or skip reasons
Process exit	number	Exits with code 1 on download failure

Dependencies

Dependency	Purpose
progress	Renders a progress bar in the terminal during download
extract-zip	Extracts the downloaded Chromium zip archive
fs-extra	File system operations (mkdir, unlink, chmod, removeSync)
https-proxy-agent	Proxy support for HTTP/HTTPS requests
proxy-from-env	Resolves proxy URL from environment variables
https / http	Node.js built-in modules for making HTTP requests

Usage Examples

Standard Installation

# Chromium is downloaded automatically during installation
npm install taiko
# Output: Downloading Chromium r123456 - 120.5 Mb [====================] 100% 0.0s
# Output: Chromium downloaded to /path/to/node_modules/taiko/.local-chromium/linux-123456

Skip Download via Environment Variable

# Skip Chromium download when a system browser is available
TAIKO_SKIP_CHROMIUM_DOWNLOAD=true npm install taiko
# Output: Skipping Chromium Download as given in environment variable.

Skip Download via npm Config

# Skip via npm config (useful in .npmrc files)
npm config set taiko_skip_chromium_download true
npm install taiko
# Output: Skipping Chromium Download as given in npm config.

Use Custom Browser Path

# Point Taiko to a pre-installed Chromium/Chrome binary
TAIKO_BROWSER_PATH=/usr/bin/chromium-browser npm install taiko

Behind a Corporate Proxy

# Download through a proxy server
HTTPS_PROXY=http://proxy.example.com:8080 npm install taiko

Related Pages

Implements Principle

Principle:Getgauge_Taiko_Browser_Installation

Requires Environment

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