How Can I Reliably Detect User Browsers Without Using User Agent Strings?

Detecting User Browsers without User Agent Strings

Recognizing Browser Types

When developing extensions for multiple browsers, it's crucial to accurately identify the user's browser to redirect them to the corresponding download page. However, relying on the User Agent string for browser detection is unreliable due to its vulnerability to spoofing.

Duck-Typing for Accurate Browser Detection

To address this, a duck-typing approach is employed. Duck-typing focuses on the behavior and properties of the browser, rather than relying on a specific signature or identification string. This method is more robust and less susceptible to spoofing.

Demo and Implementation

In the provided JavaScript code, various checks are performed to identify the common browsers, including Firefox, Chrome, Safari, Opera, IE, Edge, and Edge Chromium. Each check examines the browser's unique characteristics, ensuring accurate detection.

Feature Detection over Browser Detection

While browser detection is sometimes necessary, it's generally recommended to prioritize feature detection when possible. Feature detection involves checking for the presence or absence of specific browser capabilities, ensuring better robustness and compatibility with future browser versions.

Code Sample

The following code snippet provides the duck-typing-based browser detection method:

// Duck-typing browser detection

var isFirefox = typeof InstallTrigger !== 'undefined';
var isChrome = !!window.chrome && (!!window.chrome.webstore || !!window.chrome.runtime);
var isSafari = /constructor/i.test(window.HTMLElement) || (function (p) { return p.toString() === "[object SafariRemoteNotification]"; })(!window['safari'] || (typeof safari !== 'undefined' && window['safari'].pushNotification));
var isOpera = (!!window.opr && !!opr.addons) || !!window.opera || navigator.userAgent.indexOf(' OPR/') >= 0;
var isIE = /*@cc_on!@*/false || !!document.documentMode;
var isEdge = !isIE && !!window.StyleMedia;
var isEdgeChromium = isChrome && (navigator.userAgent.indexOf("Edg") != -1);
var isBlink = (isChrome || isOpera) && !!window.CSS;

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