Implementation:SeleniumHQ Selenium Closure UserAgent

Knowledge Sources	SeleniumHQ_Selenium Google Closure Library
Domains	JavaScript_Atoms, Vendored_Library
Last Updated	2026-02-12 00:00 GMT

Overview

Vendored Google Closure Library module providing rendering engine and browser detection via user agent string parsing.

Description

Rendering engine detection utilities. Exposes compile-time constants and runtime checks for browser engines (IE, Edge/EdgeHTML, Gecko, WebKit, Opera/Presto) and platforms (mobile). Supports compile-time assumptions (ASSUME_IE, ASSUME_GECKO, etc.) for dead-code elimination by the Closure Compiler. For browser brand detection (Safari vs Chrome), see goog.userAgent.product.

Usage

Consumed internally by Selenium's JavaScript atoms build system.

Code Reference

Source Location

• Repository: SeleniumHQ_Selenium
• File: third_party/closure/goog/useragent/useragent.js

Key Exports

goog.provide('goog.userAgent');

// Compile-time assumption flags
goog.userAgent.ASSUME_IE
goog.userAgent.ASSUME_EDGE
goog.userAgent.ASSUME_GECKO
goog.userAgent.ASSUME_WEBKIT
goog.userAgent.ASSUME_MOBILE_WEBKIT
goog.userAgent.ASSUME_OPERA

// Runtime detection constants
goog.userAgent.OPERA     // Presto-based Opera
goog.userAgent.IE        // Internet Explorer
goog.userAgent.EDGE      // EdgeHTML-based Edge
goog.userAgent.EDGE_OR_IE
goog.userAgent.GECKO     // Firefox/Gecko engine
goog.userAgent.WEBKIT    // WebKit engine
goog.userAgent.MOBILE    // Mobile browser
goog.userAgent.SAFARI    // Alias for WEBKIT

// Functions
goog.userAgent.getUserAgentString = function() { ... };
goog.userAgent.getNavigator = function() { ... };

Related Pages

• Environment:SeleniumHQ_Selenium_Contributor_Development_Environment