Parsed from your User-Agent string using UAParser.js
1. Technical Classification
Derived DataUser-Agent ParsingVersion IdentifierFingerprinting Signal
Browser version is extracted from the User-Agent string and indicates the specific release of your browser. This identifier reveals:
Feature support: Which web APIs and standards your browser supports
Security posture: Whether you're running an up-to-date, secure version
Update habits: How frequently you update your browser
Unique identifier: Combined with other data, creates a precise fingerprint
2. Background & Purpose
Browser versioning became critical as the web evolved rapidly in the 1990s and 2000s. Each browser version introduced new features, fixed bugs, and changed behavior. Websites needed to know the exact version to serve compatible code.
Version Number Schemes
Different browsers use different versioning systems:
Semantic Versioning (Major.Minor.Patch)
Example: Firefox 121.0.1
Major (121): Significant changes, potentially breaking
Minor (0): New features, backward compatible
Patch (1): Bug fixes, security updates
Chromium's Rapid Release Cycle
Example: Chrome 120.0.6099.129
Chrome increments the major version every 4 weeks (since 2021), leading to version numbers like 120, 121, 122 in quick succession.
Major: Shipped every ~4 weeks
Build numbers: More granular internal versioning
Safari's Dual Versioning
Example: Safari 17.1 (WebKit 605.1.15)
Safari reports both the browser version and the underlying WebKit version, which can be confusing for parsing.
Why Version Detection Matters
Feature detection: Knowing if specific APIs are available (e.g., WebP support in Chrome 23+)
Bug workarounds: Avoiding known issues in specific versions
Security: Identifying vulnerable versions that should be blocked
Analytics: Understanding how quickly users adopt new versions
3. Version Examples & Patterns
Current Versions (as of 2024-2025)
Browser
Version Format
Current Range
Release Frequency
Chrome
120.0.6099.129
120-123
Every 4 weeks
Firefox
121.0
120-122
Every 4 weeks
Safari
17.1
16-17
Major: Yearly, Minor: Quarterly
Edge
120.0.2210.61
120-123
Every 4 weeks (follows Chrome)
Historical Versions
Internet Explorer (Discontinued)
Versions: IE 6 (2001) → IE 11 (2013)
IE support officially ended in June 2022, but some users still run it on old systems.
Legacy Edge (EdgeHTML)
Versions: 12-18 (2015-2019)
Old Edge used Microsoft's proprietary engine before switching to Chromium.
Evergreen vs Fixed Versions
Evergreen browsers: Auto-update to latest version (Chrome, Firefox, Edge, Safari)
Most users run recent versions
Version distribution is tight (within ~5 versions)
Fixed versions: Require manual updates or system upgrades
Corporate environments often lock versions
Some users intentionally disable updates
Creates long tail of old versions
4. Common Legitimate Uses
1. Feature Availability Checks
Use case: Determine if specific web features are supported
Use case: Block or warn users on vulnerable browser versions
// Block ancient versions with known security holes
if (browserName === 'Internet Explorer' ||
(browserName === 'Chrome' && version < 100)) {
showSecurityWarning('Your browser is outdated and unsafe');
}
3. Bug-Specific Workarounds
Use case: Apply fixes for known bugs in specific versions
Safari 15.4 had a localStorage bug affecting authentication
Firefox 88 had issues with some SVG rendering
Chrome 96 had video playback issues on certain hardware
4. Analytics & Support Decisions
Use case: Understand your user base's update habits
Version distribution: See how spread out your users are
Update adoption: Track how fast users upgrade
Support cutoff: Decide when to drop support for old versions
5. Progressive Enhancement
Use case: Provide enhanced features to newer browsers
// Enable WebP images in Chrome 23+
if (browserName === 'Chrome' && version >= 23) {
useWebPImages();
} else {
useJPEGImages();
}
5. Version Detection Challenges
Mobile vs Desktop Versions
The same browser may have different version numbers on mobile vs desktop:
Platform
Chrome Version
Update Frequency
Chrome Desktop
120.x
Every 4 weeks
Chrome Android
120.x
Every 4 weeks (same as desktop)
Safari iOS
17.x
Tied to iOS updates
Safari macOS
17.x
Independent updates
OS-Locked Versions
Some browsers are tied to operating system versions:
Safari on iOS
Safari on iOS can only be updated by updating iOS itself. Users on old iPhones (e.g., iPhone 6) are stuck on old Safari versions.
Examples:
iOS 12: Safari 12 (max version)
iOS 15: Safari 15 (max version)
iOS 17: Safari 17 (current)
Corporate "Locked" Versions
Many enterprises disable auto-updates for stability:
IT departments test new versions before deploying
Can result in 6-12 month delays
Creates security risks and compatibility issues
Version Freezing in User-Agent
Some browsers are "freezing" version numbers in User-Agent to reduce fingerprinting:
Chrome: Plans to freeze at version 99 or 100 in UA (use Client Hints for real version)
Brave: Already reports generic Chrome version
6. Privacy Implications & Tracking Risks
Privacy Risk: MEDIUM
Browser version is a highly identifying component of browser fingerprinting, especially when combined with other attributes.
Version as Unique Identifier
Narrow Version Windows
Most users update within days of a new release, creating temporary unique identifiers:
Day 1-3: Early adopters (5-10% of users) - highly identifiable
Day 4-14: Most users update - less unique
Day 15+: Stragglers on old version - become unique again
Combined Fingerprinting
Version is rarely used alone, but combined with:
Browser + Version + OS: Very identifying (e.g., "Firefox 121 on Linux")