Environment Context

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getEnvContext()

Collects every available browser signal in one call and returns an EnvContext object — pass it to parseUA({ ctx }) to enable multi-signal detection.

import { getEnvContext } from 'ua-browser'

getEnvContext(): Promise<EnvContext>

Returns: Promise<EnvContext>

Signals it collects:

Category	Signals
Client Hints	platform, platformVersion, architecture, fullVersionList
WebGL	GPU renderer + vendor, max texture size, compressed texture formats (ASTC/ETC2/PVRTC/S3TC)
Screen	devicePixelRatio, screenWidth, screenHeight
CSS env	safe-area-inset-top (iOS notch / Dynamic Island)
Hardware APIs	hardwareConcurrency, deviceMemory, Vibration API, DeviceMotion events
Input	pointerType (coarse/fine/none), hover capability
Network	connection.effectiveType, connection.saveData
Audio	Sample rate
Fonts	OS-specific font availability probe
iOS 26	CSS feature detection (isIOS26Plus) to correct the frozen UA on iOS 26+

iOS 26 version detection

Since iOS 26, Apple freezes CPU iPhone OS in the UA at 18_7, so pure UA parsing reports the wrong system version. getEnvContext() confirms iOS 26+ through CSS feature detection and corrects osVersion to '26' (the major version).

For the exact minor version (26.0–26.5), use probeIOS26Version().

Example:

import { getEnvContext, parseUA } from 'ua-browser'

const ctx = await getEnvContext()
const result = parseUA(navigator.userAgent, { ctx })

console.log(result.device)   // 'Mobile' — correct even in desktop mode
console.log(result.arch)     // 'arm64' (Apple Silicon) or 'x86_64' (Intel)
console.log(result.language) // 'zh-CN'

Notes:

• Browser only. Safe to call in Node.js — every DOM access is guarded, undefined is returned, and the result is equivalent to getNavContext().
• Each DOM API is wrapped in its own try/catch, so a single denied permission does not block the remaining signals.
• If you don't need to reuse the ctx object, uaBrowser.detect() is simpler.

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getNavContext()

Reads the current browser's navigator and returns a NavContext object. In Node.js it returns a safe empty object, so callers need no environment checks.

import { getNavContext } from 'ua-browser'

getNavContext(): NavContext

Returns: NavContext

Example:

const nav = getNavContext()
const result = parseUA(navigator.userAgent, { nav })

console.log(result.language) // 'zh-CN'
console.log(result.platform) // 'Win32'

Notes:

• When you also need architecture or device-precision signals, prefer getEnvContext().
• getNavContext() is synchronous; getEnvContext() is asynchronous.

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getWindowsVersion(nav)

Fetches the exact Windows version asynchronously, to tell Windows 10 from Windows 11 — their UA strings are identical (Windows NT 10.0).

import { getWindowsVersion, getNavContext, parseUA } from 'ua-browser'

getWindowsVersion(nav: NavContext): Promise<string | null>

Parameter	Type	Required	Description
nav	NavContext	Yes	Browser context; pass the return value of getNavContext()

Returns: Promise<string | null> — a version string (such as '11', '10'), or null when unavailable

Example:

const nav = getNavContext()
const windowsVersion = await getWindowsVersion(nav)
const result = parseUA(navigator.userAgent, { nav, windowsVersion })

console.log(result.osVersion) // '11' or '10'

Notes:

• Requires navigator.userAgentData.getHighEntropyValues() (Chrome 90+, Edge 90+).
• Returns null on Firefox, Safari, and Node.js, in which case osVersion falls back to the UA-derived value.
• getEnvContext() calls this internally; use it standalone only when you need NavContext-level context without paying for a full EnvContext.

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getLanguage(nav)

Extracts a normalized browser language from a NavContext. Normalizes the tag to BCP 47 form (e.g. 'en-us' → 'en-US', 'ZH_CN' → 'zh-CN').

import { getLanguage, getNavContext } from 'ua-browser'

getLanguage(nav: NavContext): string

Parameter	Type	Required	Description
nav	NavContext	Yes	Browser context

Returns: string — normalized language tag such as 'zh-CN' or 'en-US'; 'unknown' when unavailable.

Example:

const nav = getNavContext()
console.log(getLanguage(nav)) // 'zh-CN'

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probeIOS26Version()

Probes the exact iOS 26 minor version through CSS / JavaScript feature detection. Returns '26.0'–'26.5', or null outside an iOS 26+ environment.

Requirement: this function is only meaningful in a browser. It always returns null in Node.js.

import { probeIOS26Version } from 'ua-browser'

probeIOS26Version(): string | null

Returns: string | null

How it decides:

Return value	Evidence
'26.5'	The Origin API exists (new in Safari 26.5)
'26.4'	PerformanceResourceTiming.finalResponseHeadersStart exists
'26.3'	NavigateEvent.prototype.signal exists
'26.2'	Math.sumPrecise exists
'26.0'	CSS.supports('animation-timeline', 'view()') is true
null	Not Safari/WebKit 26+ (iOS 18 or earlier)

Example:

import { probeIOS26Version, getEnvContext, parseUA } from 'ua-browser'

// Option B: getEnvContext corrects osVersion to '26' (the major version) automatically
const ctx = await getEnvContext()
const result = parseUA(navigator.userAgent, { ctx })
console.log(result.osVersion) // '26' on iOS 26+

// Option A: the exact minor version
const exact = probeIOS26Version()
console.log(exact) // '26.5', '26.4', '26.3', '26.2', '26.0', or null

TIP

The two work best together: parseUA handles every field, and probeIOS26Version() is called separately when you need an exact iOS 26 minor version.

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