Connection Type

Technical Classification

Type: JavaScript Property (navigator.connection.effectiveType)

Data Source: Browser's Network Information API

When Available: Chromium-based browsers (Chrome, Edge, Opera, Brave), limited support in other browsers

Return Type: String ('slow-2g', '2g', '3g', '4g')

Background & Purpose

The navigator.connection.effectiveType property is part of the Network Information API. It returns a string representing the effective connection type based on recent observed network performance, not the actual connection technology.

Historical Context:

Introduced as part of the W3C Network Information API specification
Designed to help developers optimize content delivery based on connection speed
Based on observed round-trip time and downlink values, not reported radio technology
Primarily implemented in Chromium-based browsers
Firefox and Safari have limited or no support for this API
Enables adaptive loading strategies for modern web applications

Key Characteristics:

Represents effective network quality, not actual technology (e.g., 5G connection may report as 4g if slow)
Based on real network measurements over recent period
Updates dynamically as network conditions change
Intentionally simplified to four categories

Connection Type Values

Four Possible Values:

Type	Typical RTT	Typical Downlink	Description
`slow-2g`	> 2000ms	< 50 kbps	Extremely slow connection, barely usable for web browsing. May indicate poor cellular signal or heavily throttled connection.
`2g`	1400-2000ms	50-70 kbps	Slow connection typical of 2G cellular networks (EDGE/GPRS). Basic browsing possible but media loading is very slow.
`3g`	270-1400ms	70-700 kbps	Moderate connection typical of 3G networks (HSPA). Suitable for most web browsing, slow for HD video.
`4g`	< 270ms	> 700 kbps	Fast connection typical of 4G LTE, 5G, cable, or fiber. Suitable for HD video streaming and large downloads.

Important Notes:

Not Actual Technology: A 5G connection with poor signal might report as '3g'
Wi-Fi Detection: Wi-Fi typically reports as '4g' if fast, but can report lower if congested
Ethernet: Wired connections almost always report as '4g'
Dynamic Updates: Value changes as network conditions change
Conservative Estimates: Browser may report lower speed to be safe

Real-World Examples:

Fast home Wi-Fi: '4g'
Congested public Wi-Fi: '3g' or '2g'
5G urban area: '4g'
LTE with weak signal: '3g'
Tethered connection with data limit: '2g' or '3g'

Common Uses

Legitimate Uses:

Adaptive Content Loading: Serve lower-resolution images on slow connections
Progressive Enhancement: Load basic content first, then enhance for fast connections
Video Quality Selection: Auto-select appropriate video resolution (480p vs 1080p)
Resource Prioritization: Defer non-critical assets on slow connections
User Experience: Warn users before large downloads on slow connections
Preloading Strategy: Only preload content on fast connections
Analytics: Understand user experience based on connection quality
A/B Testing: Segment users by connection speed for experiments

Example Implementation:

YouTube and Netflix use similar data to select default video quality
News sites may show text-only mode for 'slow-2g' or '2g'
Image-heavy sites can serve WebP or lower resolution on slower connections
Web apps can disable auto-play videos on '3g' or slower

Platform Differences

Browser Support:

Browser	Support	Notes
Chrome	Yes (v61+)	Full support, most reliable implementation
Edge	Yes (v79+)	Full support on Chromium-based Edge
Opera	Yes (v48+)	Full support
Brave	Yes	Chromium-based, full support
Firefox	No	Not implemented; `navigator.connection` returns undefined
Safari	No	Not implemented; `navigator.connection` returns undefined
Mobile Chrome	Yes	Works on Android
Mobile Safari	No	Not supported on iOS

Detection Code:

Always check for API availability before use:

if (navigator.connection && navigator.connection.effectiveType)
Provide fallback behavior for unsupported browsers
Consider using feature detection libraries

Why Limited Support?:

Privacy concerns in Firefox and Safari communities
Potential for fingerprinting and user tracking
Concerns about exposing too much device/network information
W3C specification progress has been slow

Privacy Implications

Tracking Risk: LOW-MEDIUM

Privacy Concerns:

Device Type Inference: Mobile users more likely to show cellular speeds vs desktop users
Location Context: Rural areas more likely to have slower connections
Economic Profiling: Connection speed may correlate with socioeconomic status
Fingerprinting Component: Adds entropy when combined with other attributes
Behavioral Tracking: Patterns of connection type changes reveal mobility
Time-Based Correlation: Changes from 4g to 3g during day might indicate commuting patterns

Why Low-Medium Risk:

Only four possible values (low uniqueness on its own)
Most desktop users consistently report '4g'
Not supported in Firefox or Safari (limits cross-browser tracking)
Less identifying than timezone, screen resolution, or canvas fingerprint
Value changes frequently, reducing reliability for long-term tracking
Primarily useful for analytics, not individual tracking

Combined Fingerprinting Risk:

Adds minimal entropy to fingerprint (2 bits of information)
More useful for correlation than identification
Can reveal device context (mobile vs desktop) when combined with screen size

User Control & Protection

How to Control or Hide Connection Type:

Browser Settings:

Firefox/Safari: No action needed - not supported
Chrome/Edge: No built-in setting to disable; requires extension
Brave: May limit or randomize this data in aggressive privacy modes

Privacy Extensions:

Some fingerprint protection extensions can block or spoof navigator.connection
Canvas Defender, Trace, and similar tools may modify this value
Check extension documentation for Network Information API spoofing

Developer Tools:

Chrome DevTools: Network tab > Throttling allows simulating different connection types
Useful for testing but doesn't affect effectiveType value
Some extensions can override JavaScript APIs

Testing Current Value:

Open browser console and type: navigator.connection?.effectiveType
Will return undefined if not supported
Otherwise returns one of the four string values

Limitations of Control:

No native browser option to disable in Chrome/Edge
Blocking entire API may break adaptive loading features
Spoofing value may cause sites to serve inappropriate content
Limited practical privacy benefit due to low uniqueness

Privacy Best Practices:

Use privacy-focused browsers (Firefox, Safari) that don't expose this API
Accept that on fast connections, '4g' is extremely common
Focus on higher-impact privacy protections (VPN, ad blockers, etc.)
Consider browser fingerprinting protection extensions if concerned

Additional Resources

MDN: NetworkInformation.effectiveType
Comprehensive documentation for the effectiveType property
MDN: Network Information API
Overview of the entire Network Information API
W3C: Network Information API Specification
Official specification draft for the API
Web.dev: Adaptive Loading
Guide to building sites that adapt based on network conditions
Can I Use: Network Information API
Browser compatibility table for Network Information API
Google Developers: Save-Data
Related API for detecting user preference for reduced data usage

Your Current Connection Type