The probe runs once per session in the browser. It collects device signals using standard browser APIs, then POSTs them to your server's probe endpoint. A session cookie prevents repeated collection.

Browser                                      Server
  │                                            │
  │  collectSignals()                          │
  │  getBattery()                              │
  │                                            │
  │  POST /device-router/probe                 │
  │  ─────────────────────────────────────>    │
  │  { hardwareConcurrency: 8,                 │
  │    deviceMemory: 8, ... }                  │
  │                                            │
  │  { sessionToken: "abc123" }                │
  │  <─────────────────────────────────────    │
  │                                            │
  │  Set cookie: device-router-session=abc123  │
  └────────────────────────────────────────────┘

Usage

Script tag (IIFE)

The simplest approach — include the pre-built bundle:

<script src="/device-router-probe.min.js"></script>

The probe auto-executes on load. Serve the file from dist/device-router-probe.min.js.

Auto-injection

Middleware packages can auto-inject the probe into HTML responses:

const { middleware, probeEndpoint, injectionMiddleware } = createDeviceRouter({
  storage,
  injectProbe: true,
});

Programmatic

import { runProbe } from '@device-router/probe';

await runProbe({
  endpoint: '/device-router/probe', // default
  cookieName: 'device-router-session', // default
  cookiePath: '/', // default
});

Programmatic with retry

import { runProbeWithRetry } from '@device-router/probe';

await runProbeWithRetry({
  endpoint: '/device-router/probe',
  retry: {
    maxRetries: 3, // default: 3
    baseDelay: 500, // default: 500ms
    maxDelay: 5000, // default: 5000ms
  },
});

Uses exponential backoff with jitter on network failure. Signals are collected once before the retry loop. Does not affect the IIFE bundle size.

Signals collected

Signal	API	Browser Support
CPU cores	`hardwareConcurrency`	All modern browsers
Device memory	`deviceMemory`	Chromium
Connection info	`navigator.connection`	Chromium
User agent	`navigator.userAgent`	All browsers
Viewport dimensions	`window.innerWidth/Height`	All browsers
Pixel ratio	`devicePixelRatio`	All browsers
Prefers reduced motion	`matchMedia`	All modern browsers
Color scheme	`matchMedia`	All modern browsers
GPU renderer	WebGL debug info	Most browsers
Battery status	`navigator.getBattery()`	Chromium