Browser Feature Detection

Ever noticed how some websites “just know” if your browser can play a certain video, support dark mode, or run advanced animations? That’s not a lucky guess—it’s browser feature detection in action. 

But beyond enhancing user experience, these detection methods have a hidden side: they can also be used to identify your browser and even help track you across the web. If you’re interested in privacy, multiaccount management, or web automation, understanding browser feature detection is essential.

What is Browser Feature Detection?

Browser feature detection is the process by which websites or web applications check which functionalities or APIs your browser supports. Instead of assuming your browser works a certain way, scripts actively “probe” your browser to see if it supports features like video codecs, CSS properties, JavaScript APIs, or even hardware access.

While originally designed to improve compatibility (so websites can adapt to different browsers), feature detection is also a popular component in browser fingerprinting, helping sites uniquely identify and track users—even across sessions or profiles.

How Does Browser Feature Detection Work?

Websites typically use JavaScript (and sometimes CSS or HTML) to test for browser features:

1. JavaScript Probing

Scripts run checks like:

if (‘geolocation’ in navigator) { /* Geolocation is supported */ }

if (window.WebGLRenderingContext) { /* WebGL is supported */ }

These checks reveal supported APIs and features.

2. CSS Support Checks

Websites can test for CSS properties:

if (CSS.supports(‘display’, ‘grid’)) { /* CSS Grid is supported */ }

3. HTML Element Detection

Creating and checking support for new HTML tags or attributes:

if (‘autoplay’ in document.createElement(‘video’)) { /* Video autoplay supported */ }

4. Hardware & Media Capabilities

Detecting access to features like:

• Camera and microphone
• Touch screen support
• Audio output devices
• Specific video or audio codecs

5. Advanced Feature Libraries

Libraries like Modernizr automate and expand feature detection, running hundreds of checks at once.

Why Does Browser Feature Detection Matter?

• Enhanced compatibility: Lets websites tailor user experiences (e.g., fallback if a feature isn’t supported).
• Enables progressive enhancement: Users get the best experience possible for their device/browser.
• Fingerprinting risk: The exact combination of supported and unsupported features is highly unique, making feature detection a powerful tracking vector.
• Multiaccount management risk: Anti-bot systems may use feature detection to link seemingly separate browser profiles or sessions—flagging multiaccount activity or bots.

Browser Feature Detection vs. Browser Fingerprinting

How to Minimize Browser Feature Detection Risks

• Use anti detect browsers like Multilogin: Each profile can spoof or randomize feature support, breaking linkability across accounts.
• Customize feature support: Advanced anti detect browsers let you fine-tune which features are “present” or “absent” per profile.
• Combine with residential proxies: Using providers like NodeMaven ensures your network traffic matches your device and feature profile.
• Rotate browser profiles: Never reuse the same profile for multiple accounts—each should look unique in features and environment.
• Avoid simple privacy modes: Incognito mode or VPNs do NOT change your browser’s feature signature.

Browser Feature Detection and Anti Detect Browsers

Anti detect browsers like Multilogin are built to defeat feature-based tracking:

• Profile-level spoofing: Each browser profile can present a different set of supported features (APIs, CSS, codecs, etc.).
• Canvas, WebGL, AudioContext spoofing: Masks or randomizes low-level features often probed by trackers.
• Seamless proxy integration: Each profile can use its own NodeMaven residential proxy, keeping the network and browser “story” consistent.
• Powerful for multiaccounting and automation: Makes your automation or multiple accounts appear as truly unique, separate users—evading advanced anti-bot and anti-fraud systems.